Geography-Paper-VI-Tools-and-Techniques-in-Geography-for-Spatial-Analysis-I-munotes

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MAP PROJECTIONS
After going through this chapter you will be able to understand the
following features:
Unit Structure
1.1 Objectives
1.2 Introduction
1.3 Subject discussion
1.4 Concept of Map Projections
1.5 Need for Map Projections
1.6 Classification and suitability of Map Projections
1.7 Construction and properties Map Projections
1.8 Graphical methods of drafting selected projections
1.9 The different types of projection
1.9.1 Zenithal polar equal area
1.9.2 Zenithal equidistant
1.9.3 Conical one standard parallel
1.9.4 Conical two standard parallel
1.9.5 Cylindrical equal area
1.9.6 Cylindrical equidistant
1.10 Summary
1.11 Check your Progress/Exercise
1.12 Answers to the self-learning questions
1.13 Technical words and their meaning
1.14 Task
1.15 References for further study


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2 1.0 OBJECTIVES
 By the end of this unit you will be able to:
 Discu ss the Concept of Map Projections
 Understand the Need for Map Projections
 Learn the Classification and suitability of Map Projections
 Understand the Construction and properties of Map Projections
 Learn Graphical methods of drafting selected projections
 Learn Zenithal polar equal area
 Learn Zenithal equidistant
 Learn Conical one standard parallel
 Learn Conical two standard parallel
 Learn Cylindrical equal area
 Learn Cylindrical equidistant
1.2. INTRODUCTION
In this unit we w, will study Projections its concept, need, classification
and suitability, construction and properties. We will learn about Graphical
methods of drafting selected projections such as Zenithal polar equal area,
Zenithal equidistant, Conical one standard parallel, Conical two standard
parallel Clin Cylindrical equal area, Cylindered Rica and l equidistant in
the latter part of this unit.
1.3. SUBJECT -DISCUSSION
A reduced model of the Earth that may be a globe or a map is essential
for any study in geography. But neither of the two is perfect, as a globe is
seldom practical, and flat maps are never free from errors. Maps are
important and indispensable tools to geographers that help them
understand important things about the surface of the Earth in a visual way.
It is a two dimensional description of a specific area of land. Maps
describe in a visual or graphic format certain key features of the territory
being examined. A map projection is a systematic transformation of the
latitudes and longitudes of locations from the surface of a sphere or an
ellipsoid into locations on a plane. Maps cannot be created without map
projections. All map projections necessarily distort the surface in some
fashion.

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3 1.4. CONCEPT OF MAP PROJECTIONS
A map projection is a mathematical formula used to transfer all or part of
the curved surface of the earth onto the flat surface of a map.
1.5. NEED OF MAP PROJECTIONS
We know that the shape of the Earth is an oblate spheroid or an ellipsoid.
A globe is a scaled -down model of the Earth. Even though globes are
capable of representing the size, shape, distance and directions of the
Earth’s features with reasonable accuracy, they are not suitable for many
applications. They are hard to transport and store, not suitable for use at
large scales,and expensive to produce. Moreover, measuring terrain
properties is difficult on a curved surface and it is quite impossible to
view large portions of the Earth at once. Nevertheless maps do not suffer
from these shortcomings. They are more practical in most applications if
compared to globes.
So to portray a curved plane that is the globe on a 2 dimensional plane or a
map we need to construct a "projection" to alter the curved space and
make it flat. Hence to give an accurate view of the Earth in a 2D sense,
we need to project the Earth on to a refer ence point.
1.6. CLASSIFICATION AND SUITABILITY OF
MAP PROJECTIONS
Down the ages cartographers have developed innumerable map
projections among them three large families of map projections and
several smaller ones have been acknowledged. These are based on the
types of geometric shapes that are used to transfer features from a sphere
to a plane. It may be said that Map projections are based on developable
surfaces, and the three traditional families consist of cylinders, cones, and
planes. Now the question arises that which developable surface should be
used for a projection. It depends on what region is to be mapped, its
geographical extent, and the geometric properties that areas, boundaries,
and routes need to have, given the purpose of the map.
Now we have come to know that three classes of map projections are
cylindrical, conical and azimuthal. The earth's surface projected on a map
wrapped around the globe as a cylinder produces the cylindrical map
projection. Projected on a map formed into a cone gives a conical map
projection. When projected on a planar map it produces azimuthal or
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Fig showing Three classes of map projections: cylindrical, conical and
azimuthal.
1.7. CONSTRUCTION AND PROPERTIES OF MAP
PROJECTIONS
❖ The constructio n off a map projection involves three steps:
• Selection of a model for the shape of the earth or planetary body
(usually choosing between a sphere or ellipsoid)
• Transformation of geographic coordinates (longitude and latitude) to
plane coordinates (eastings and northings or x, y)
• Reduction of the scale
❖ Map projection properties:
The five essential map projection properties are shape, distance, direction,
scale, and area. These map projection properties came into being when
there is conversion from a three dimensional object, such as the earth, to a
two-dimensional representation, such as a flat paper map. Of them area
and shape are considered major properties and are mutually exclusive,
that is if area is held to its true form on a map, shape must be distorte d,
and vice versa. But distance and direction are minor properties that may
coexist with any of the other projection properties. Nevertheless, distance
and direction cannot be true everywhere on a map. A map can never
show all the map projection properties , true direction, true distance, truth
area, and true shape at the same time. It may exhibit one or more map
projection properties in one attempt.
Whenever we create a flat map of a three -dimensional object such as
earth distortions occur. But it is not constant across the map. It is
observed that distortion may take different forms in different parts of the
map like it is usually less near the points or lines of intersection where the
developable surface intersects the globe.
Different families of map proj ections aim to preserve at least one of the
map projection properties. It is discussed below:
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5  The equal area map projection , aims to preserve the area relationships
of all parts of the globe and here the meridians and parallels are not at
right angles to each other. Moreover, distance distortion is usually
present on equal area map projection, as well as shape is often skewed.
However it is useful for general quantitative thematic maps.
 The Conformal map projections , also known as orthomorphic map
projectio n, preserve angles around points, and shape of small areas. In
Conformal map projections meridians intersect parallels at right
angles, areas are distorted significantly in small scales, and shapes of
large regions may be severely distorted.
 The Mercator projection is a conformal map projection that preserves
shape.
 The equidistant map projection aims to preserve great circle distances
meaning a distance can be held true from one point to all other points,
or from a few select points, to others, but not from all points to all
other points. Identifying marks of the equidistant map projection are
that they are neither conformal nor equal area, and look less distorted.
Equidistant map projections are useful for general purpose maps and
Atlas maps.
 The azimuthal map projection , also known as the true direction map
projection, preserves direction from one point to all other points in the
map. Azimuthal map projection is most useful for preserving direction
two or one from the point, often used for navigation.
1.8. GRAP HICAL METHODS OF DRAFTING
SELECTED PROJECTIONS
Map projection is the method of transferring the graticule of latitude and
longitude on a plane surface. It can also be defined as the transformation
of a spherical network of parallels and meridians on a plane surface.
As we know that, the earth on which we live in is not flat. It is geoid in
shape like a sphere. A globe is the best model of the earth. Due to this
property of the globe, the shape and sizes of the continents and oceans
are accurately shown on it. It also shows the directions and distances
very accurately. The globe is divided into various segments by the lines of
latitude and longitude. The horizontal lines represent the parallels of
latitude and the vertical lines represent the meridians of the longitude. The
network of parallels and meridians is called graticule. This network
facilitates drawing of maps. Drawing of the graticule on a flat surface is
called projection.
But a globe has many limitations. It is expensive. It can neither be carried
everywhere easily nor can a minor detail be shown on it. Besides, on the
globe the meridians are semi -circles and the parallels are circles. When
they are transferred on a plane surface, they become intersecting straight
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6 1.9 THE DIFF ERENT TYPES OF PROJECTION USE
ARE AS FOLLOWS
1.9.1 Zenithal Polar Equal Area Projection
In this projection, a 2-dimensional plane of projection touches the
generating globe at either of the poles. The meridians are straight lines
drawn at true azimuth apart radiating from the pole. At any point the
product of the two principal scales is unity. The parallels are spaced
with varying radii in such a way that area on the projection exactly
conforms to the area on the earth’s surface.
Zenithal Polar Equal Area Project ion -
Draw Zenithal Polar Equal Area Projection with the help of following
details.
Radius of the globe = 5cm. Laditudinal distance (interval) = 15°
Longitudinal interval = 30°
Draw projection for northern hemisphere.
1) Draw circle of 5cm radius to represen t Earth
2) Latitudinal interval is 15° & so draw sever lines at the interval of
15° from Equator to Pole.

Draw lines connecting 90°N . To equator (00 ),15°, 30°, 45°, 60° & 75° as
shown in the diagram. Take these distances as radius & draw conc entric
circles to represent latitudes.




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7 N
90°


3) Longitudinal interval is 30° & so draw straight vertical line at the
center of concentric circles. Keep protractor near to this line & take angles
at an interval of 30° - i.e. 0°, 30°, 60°, 90°,120°,150°,180 °
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8 4) Give numbers to all longitudes.
Properties :-
1) The parallel are concentric circles. The pole is a point forming the
centre of this projection.
2) The meridians are straight lines radiating from the pole. They are
spaced correctly at true angular interval i.e. the azimuths are true in
this projection.
3) The meridians intersect the parallels at right angle.
4) The scale along the parallels increases away from the centre of the
projection.
5) The distance between the parallels go on decreasing away from the
centre of the projection. It means there is a decrease in the scale along
the meridians towards the margin of the projection. The decrease in the
scale along the meridians is in the same proportion in which there is
increase in the scale along the parallels away from the centre of the
projection with the result that the projection is equal area.
6) Shapes are more and more distorted away from the centre of the
projection because the scale along the meridians is too small and that
along the parallels is too large. The shape compressed along the
meridians but stretched along the parallels.
7) The shape of the central area of the projection is represented in a
satisfactory way for here the shapes are very slightly distorted.
8) Shapes are distorted away from the centre of the projection, hence
only central part of the projection can be presented in a satisfactory
way.
Advantages: -
1) It is used for preparing political and distribution maps of Polar
Regions. (Shapes of the countries in the central part are preserved).
2) Used for the general purpose maps of large areas in the northern
hemisphere.
Disadvantages: -
1) Shapes of objects are distorted more and more as you proceed from the
centre of the map outward.
2) Distances are not accurately represented except along the one or two
base p arallels (latitudes).
1.9.2 Zenithal Polar Equi -Distant Projection
In this projection, a 2 dimensional plane of projection touches the
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9 is truly maintained so that parallels are equi - distant on the meridians.
True azimuth at the pole is preserved in spacing circles while meridians
are straight lines radiating from the poles.
Draw Zenithal Polar Equidistance projection -
1) Radius of the globe = 5cm
2) Latitudinal interval = 150
3) Longitudinal interval = 300
4) Extent - Northern Hemisphere.
1) Draw circle of 5cm radius Latitudinal interval is 150. hence draw line
at the interval of 150.

2) To draw latitudes at an interval of 150 draw straight line & mark six
divisions of an interval of A - B to represent 0°,15°, 30°, 45°,
60°, 75° & 90° .

3) Take these distances as radius & draw concentric circles to represent
parallels of latitudes.
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4) Draw longitudes at an interval of 300. Give number to all parallels of
latitudes & meridian of longitude.
Properties: -
1) The parallels are concentric circles. The pole is a point forming
centre of the projection.
2) The meridians are straight lines radiating from the pole and space
correctly at true angular interval i.e. azimuths are true in this
projec tions.
3) The meridians intersect the parallels at right angles.
4) Since the spacing between the parallels represents true distancesthe
scale along the meridian is correct.
5) The scale along the parallels increases away from the centre of this
projection.
6) The areas are exaggerated and shapes distorted exaggeration and
distortion increasing away from the centre of the projection.
7) The projection is neither equal - area nor orthomorphic.
8) Shape being greatly distorted away from the centre of the projection, it
is only a small area in the central part of the projection that can be
represented in a satisfactory way. The area lying between the pole and
60 degree parallel is shown satisfactorily.
Advantages: -
1) This projection is commonly used for preparing maps of polar
areas used for general purposes.

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11 2) Since the scale along the meridians is correct, narrow strips running
along the meridians are shown fairly correctly.
Disadvantages: -
1) The distortion increases away from the equator.
2) This projection is not orthomorphic. So the shape of countries is not
same as on the globe.
1.9.3 Conical one standard parallel
A conical projection is one, which is drawn by projecting the image of the
graticule of a globe on a developable cone, which touches the globe along
aparallel of latitude called the standard parallel. As the cone touches
theglobe located along AB, the position of this parallel on the globe
coincidingwith that on the cone is taken as the standard parallel. The
length of otherparallels on either side of this parallel are distorted.
Conical one standard parallel projection 1) R = 3.2cm
2) Standa rd Parallel = 45°N .
3) Latitudinal interval = 15°
4) Longitudinal interal = 15°
5) Extent - Longitudinal - 75° E to 75°W.
Answer -
Draw circle of 3.2 cm.
Draw angles of 90° 45° N.
Draw XA line perpendicular to the line of 45°.

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12 Draw angles of 150 BYC and DYE for Latitudinal & longitudinal
intervals. Take a distance / measurement DE on the compass & draw semi
circle at Y. The line of semicircle will intersect line of 45°. From this
point draw line perpendicular to XY line. This distance GH is for our
longitudinal interval of 150 (at 45°N)
Draw straight line for drawing final projection. Mark point X Take a
distance / radius XA on the compass and draw semicircle.
A is at 45°N. Our extent is from 00 to 900N. Sol take a distance of
BC on the compass & mark divisions of 150 to the north and south of
450N. (3 - 3 divisions) Take a distance of GH on the compass & mark 5
divisions on either sides of XA line on 45°N. (Standard parallel) for
longitudes.
Draw curves from X for all markings on XA line to represent latitudes.
Draw straight lines from markings on 45°N. line to point X to represent
Latitudes.
Properties: -
1) The parallels are concentric arcs of circles. The pole is
repres ented by an arc.
2) The meridians are straight lines.
3) The meridians intersect the parallel at right angle.
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13 4) The distance between any two parallels on these projectionsis true.
Thus scale along all the meridians is correct.
5) The distance between the meridians decreases towards the poles, i.e.
the meridians are closer to each other towards the poles.
6) The scale is correct along the standard parallel but very large along
other parallels, the exaggeration increase away from the standard
parallels. Thus areas lying ad jacent to the standard parallels are fairly
correct on these projections.
7) This projection is neither equal -area nor orthomorphic.
8) The scale along the meridians is true. But it goes on increasing along
the parallels away from the standard parallel. Therefor e, away from the
standard parallel, areas are exaggerated and their shapes distorted. It
is suitable only for a narrow strip of lands lying adjacent to the
standard parallel.
Advantages: -
1) This projection is commonly used for showing areas of mid- latitudes
with limited latitudinal and larger longitudinal extent.
2) A long narrow strip of land running parallel to the standard parallel and
having east -west stretch is correctly shown on this projection.
3) Direction along standard parallel is used to show railways,
roads,narrow river valleys and international boundaries.
4) This projection is suitable for showing the Canadian Pacific Railways,
Trans -Siberian Railways, international boundaries between USA and
Canada and the Narmada Valley.
Disadvantages: -
1) It is not suita ble for a world map due to extreme distortions in the
hemisphere opposite the one in which the standard parallel is
selected.
2) Even within the hemisphere, it is not suitable for representing larger
areas as the distortion along the pole and near the equato r is larger.
1.9.4 Conical Two Standard Parallel
In this projection, a simple right circular cone is taken as the projection
plane. Two circles of the cone correspond to two different parallels on the
generating globe and form an ordinary cone independent of the globe.
These are the standard parallels which are so selected as to cover two -
thirds of the latitudinal extent of the area to be mapped. The parallels
appear as concentric arcs of circle while meridians appear as straight
lines converging at the vertex of the cone.
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14 Conical Two Standard Parallel Projection -
R = 3.2cm Standard Parallels - 40°N 10°, Longitudinal interval =15° 60°N .
Lat interval =
Extent - Lon - 90°E to 90°W -
Lat - 0° to 90°N
Draw globe with a radius of 3.2cm.

Draw XY perpendicula r line and AY, BY lines at an angles 600 & 400
respectively. Join AB points & extent lne upto the perpendicular line, to
get X point.
Draw lines AM and BN pendicular to XY line from points A & B. In
order to find out distance between A & B we can use follo wing formula
AB = 2π R × 20° → (60° − 40°)
360°
π = 3.14 R = 3.2cm
AB = 2π R × 1
18
= 1× 3.14× 3.2 × 1
9
= 3.14 × 3.2
9
= 1.1cm
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15 Draw straight vertical line take a distance of 1.1cm.

Draw lines perpendicular from A & B take measurement MA & NB on
thse lines to get points M & N. Join M, N points & extend line to get X
point. Take XA distance on the compass & draw semicircle to represent
standard parallel 600 & take XB distance on the compass & draw
semicircle to represent 400 N.

Take distance A -B = 1.1cm on straight line & draw curves on either side
with measurement of radius as 1.0cm.


We get two equal divisions of AB (latitudinal interval of 100). Mark these
divisions of 100 on the vertical line to represent latitudes from 00 to 900N.
(Use strip of paper)

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16 Draw semi circle at Y with radius equal to CD. This semicircle will
intersect YB line (400N) draw line perpendicular to XY line from this
point. (This procedure is same as conical one standard. Parallel projection)
Complete projection & give n ames to all latitudes & longitudes.

Conical Two Standard parallels projections.
Properties
1) The parallels are concentric arcs of circles. The pole is
represented by an arc.
2) The meridians are straight lines.
3) The meridians intersect the parallels at right angles.
4) The meridians are correctly divided for spacing the parallels. The
scale along all the meridians is, therefore, correct.
5) The scale is correct along the standard parallels and relatively large
along all other parallels. This projection is therefore, suitable for an
area which has small extent in latitude only. In such a case those
standard parallels are chosen which are quite close to each other. We
thus eliminated to some extent the inaccuracy caused due to different
scales of the parallels lying between the standards parallels and outside
the standard parallels.
6) A belt of an area having very small latitudinal extent but great
longitudinal extent can be shown quite satisfactorily on this projection.
7) This projection is neither equal -area nor orthomorph ic.
8) The scale being either too large or too small along the parallels other
than the standard parallels are far away from the standard parallels are
not accurately represented on this projection. Therefore, for better
representation, an area should be of s mall latitudinal extent.
Advantages: -
1) This projection is used for general purpose of maps.
2) A long narrow strip of land running in the east -west direction is shown
fairly correctly on this projection. The Canadian pacific Railway,
Trans -Siberian Railway and international boundary between U.S.A
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17 and Canada can be shown fairly accurately on this projection, the
accuracy being more than it is in the case of conical projection with
one standard parallel.
3) The projection is quite satisfactory for showing small coun tries having
small latitudinal extent.
Disadvantages: -
1) Being neither equal -area nor orthomorphic this projection is not used
for a specific purpose.
2) It is not used for displaying large areas because distortion became
greater and greater the further we move from the lines where the cone
intersects the globe.
1.9.5 Cylindrical Equal Area Projection
The cylindrical equal area projection, also known as the Lambert’s
projection, has been derived by projecting the surface of the globe with
parallel rays on a cylinder touching it at the equator. Both the parallels and
meridians are projected as straight lines intersecting one another at right
angles. The pole is shown with a parallel equal to the equator; hence,
the shape of the area gets highly distorted at the higher latitude.
R = 2cm
Lat internval = 150 Lon interval = 300 Extent = Entire world.
1) Draw circle with a radius of 2cm to represent globe. Mark
divisions of 150 (Latitudinal interval)

2) Draw perpendicular line at equator and transfer all markings for
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3) Our longitudinal extent is the entire world. Hence the total length
of circumference of globe can be calculated using formula
= 2π R
π = 3.14
= 2π R
R = 2cm
= 2× 3.14× 2
= 12.56 cm
= 12.6cm
4) Rough diagr am of our projection.

5) Our longitudinal interval is 300. We an draw rough diagram to know
total number of divisions (Total 12 divisions).

6) Divide line of 12.6cm into 12 equal parts as shown in cylindrical
equidistant projection
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7) Draw rectangle of 12.6cm X 4cm and transfer divisions from AC line
(latitudes) and from AB line (longitudes) to get cylindrical equal area
projection.
Properties
1) All the parallels are of the same length and every one of them is equal
to the length of equator.
2) The Length of equat or on this projection is equal to the length of the
equator on the globe. Therefore, the scale along the equator is correct. The
parallels are longer then the corresponding parallels on the globe. For an
example, 30 degree parallel, 60 degree parallel and 80 degree parallel
on this projection are
1.154 times, 2.000 times, and 5.758 times longer than the corresponding
parallel on the globe respectively. A pole which is the point on the globe
is equal to the length of the equator on this projection. The scale along
the parallels is, therefore, exaggerated, the exaggeration increasing away
from the equator.
3) All the meridians are of the same length and the length of each
meridian is equal to the length of the diameter of the globe but their
lengths between the p arallels go on decreasing towards the poles. Thus,
the meridians on this projection are shorted in the length than the
corresponding meridians on the globe. Their lengths have been shortened
in the same ratio in which the parallels are made longer with the result that
area of a strip lying between any two parallels on this projection is equal
to the area between the corresponding parallels on the globe. Thus, equal -
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20 area property is maintained over the entire projection. Therefore, this
projection is an equal-area and useful for showing distribution of
products.
4) In the polar area, the parallels are markedly stretched in the east-west
direction and the meridians are shortened greatly in the north -south
direction. Consequently the countries are stretched in the east-west
direction and compressed in the north -south direction. Thus, there is
increased distortion in the shapes of the countries towards the poles. The
distortion in the shapes of tropical countries is almost negligible.
5) Parallels and meridians are straight lines.
6) The meridians intersect the parallels at right angles.
7) The distances between the parallels go on decreasing towards the poles
but the distances between the meridians remain the same.
Advantages
1) This projection is used for showing tropical countries.
2) Being an equal -area projection, it is drawn mainly for showing the
world distribution of tropical products such as rubber, coconut, rice,
cotton, groundnut, etc.
Disadvantages
1) Distortion increases as we move towards the pole.
2) The projection is non-orthomorphic.
3.) Equality of area is maintained at the cost of distortion in shape.
1.9.6 Cylindrical Equi -Distant Projection
This projection is very simple to construct because it forms a grid of equal
rectangles. Because of its simple calculations, its usage was more
common in the past. In this projection, the Polar Regions are less distorted
in scale and area
Draw cylindrical Equi -distance Projection.
1) Radius of the reduced globe = 3.2cm.
2) Latitudinal interval = 150
3) Longitudinal interval = 300
4) Extent - Latitudi nal - 750N Latitude to 750S Latitude Longitudinal
extent 600 W to 600 E

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21 Procedure -
1) Draw rough diagram for understanding extent of the map.

3) For latitudinal extent find out measurement of distance B-C & for
longitudinal extent A -B.
R = 3.2cm
= 2π R
π = 3.14
AB = 2π R × 120
360

Distance AB covers angular distance of 120 ° on the earth’s surface.
AB = 2π R × 120
360
= 2 × 3.14 × 3.2 × 1
3
= 2 × 3.14× 3.2
3
= 20.09 6
3
= 6.7cm
BC = 2π R × 150
360
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= 2× 3.14 × 3.2× 150
360
= 1× 3.14× 3.2 × 5
6
= 3.14 × 3.2 × 5
6
= 50.24
6
= 8.37 cm BC = 8.4cm

4) Latitudin al extent BC = 6.4cm Longitudinal extent AB = 6.7cm.
Draw rectangle of 8.4× 6.7cm

5) Our latitudinal interval is 150. Let us draw rough diagram

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Latitudinal extent 750N to 750S. (10 Parts) Our Longitudinal interval is
300

Longitudinal extent 600W to 600E (4 parts)
6) In order to mark divisions for latitudes, draw line of 8.4cm and diide
it into 10 equal parts. Similarly for longitudes, draw line of 6.4cm &
divide it into 4 equal parts.
7) Longitudinal extent 750N to 750S Draw line of 8.4cm.
Draw lines / angle s at 300 at B & C as shown in the diagam.

Mark 10 divisions of one cm each on BE and CF lines.

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24

Join these divisions to get 10 equal parts of BC.
8) Latitudinal extent - 600W to 600.
Draw line of 6.4 cm

Draw line / angles at 300 at A & B as shown in the diagram.

Mark 4 divisions of 2cm each on A,G and BH lines.
Join these divisions to get 4 equal parts of AB.

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25 9) Draw rectangle of 8.4cm x 6.4 cm.


Now transfer four equal divisions on AB line & ten equal divisions on BC
line with the help of strip of paper.
Keep paper strip attached to line BC in (7) mark ten divisions on paper.
Now transfer paper to our final diagram and transfer all divisions on BC
line in final diagram.
Similarly transfer four equal divisions on AB line.

Cylindrical equi-distance projection.
Properties :
1) Parallels and meridians are straight lines.
2) The meridians intersect the parallels at right angles.
3) The distances between the parallels and those between the meridians
remain the same throughout the projection.
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26 4) All the parallels are of the same length and every one of them is equal
to the length of equator.
5) The Length of equator on this projection is equal to the length of the
equator on the globe. Therefore, the scale along the equator is correct. The
parallels are longer than the corresponding parallels on the globe. For an
example, 30 degree parallel,60 degree parallel and 80 degree parallel
on this projection are 1.154 times, 2.000 times, and 5.758 times longer than
the corresponding parallel on the globe respectively. A pole which is the point
on the globe is equal to the length of the equator on this projection.
Therefore the scale along the parallels isexaggerated and the exaggeration
increases away from the equator.
6) Shapes are more and more distorted away from the centre of the
projection because the scale along the meridians is too small and that
along the parallels too large. The shapes are compressed along the
meridians but stretched along the parallels.
7) The shapes of the central areas of the projection are represented in a
satisfactory way for the shapes are distorted here but very slightly.
8) Shapes being distorted away from the centre of the projection, it is
only the central part of the projection that can be represented in a
satisfactory way.
9) Generally, the area lying betwee n a pole and 45 degree parallel can be
shown on this projection satisfactorily.
Advantages :
1) It is used for preparing political and distribution maps of polar region.
(shapes of the countries in the central part are preserved).
2) Used for the general purpose maps of large areas in the Northern
Hemisphere.
Disadvantages: -
1) The distortion increases away from the equator.
2) This projection is not orthomorphic. The shape of countries is not
same as on the globe.
1.10 SUMMARY:
After going through the chapter we have come to know that map
projection is a mathematical formula used to transfer all or part of the
curved surface of the earth onto the flat surface of a map. Earth is
represented as a sphere and the process of flattening the earth causes
distortions in one or more of the following spatial properties such as: a.
Distance, b. Area, c. Shape, d. Direction. We have also learnt that no
projection is capable of preserving all these properties. Hence all flat
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27 projections and each is distinguished by its suitability for representing a
particular portion and amount of the earth's surface. Some map projections
minimize distortion in one property at the expense of another, while
others strive to balance the overal l distortion. Cartographers decide which
properties are most important and choose a projection that suits their needs.
We have studied different types of projection such as Zenithal polar equal
area, Zenithal equidistant, Conical one standard parallel, Conical two
standard parallel, Cylindrical equal area and Cylindrical equidistant.
1.11 CHECK YOUR PROGRESS/ EXERCISE
1. True false
a. A globe is a scaled down model of the Earth.
b. To portray a conical plane on a 2 dimensional plane or a map we need
to construct a "proje ction" to alter the curved space and make it flat.
c. The earth's surface projected on a map wrapped around the globe as a
cone produces the cylindrical map projection.
d. In Zenithal Polar Equal Area Projection the parallel are concentric
circles and the pole is a point forming the centre of this projection.
e. Conical one standard parallel projection is commonly used for
showing areas of low-latitudes with larger latitudinal and limited
longitudinal extent.
2. Fill in the blanks
a. A long narrow strip of land running in the east-west direction is shown
fairly correctly on projection.
b. In _ Projection all the parallels are of the same length and every
one of them is equal to the length of equator.
c. In Cylindrical Equal Area Projection all the are of the same length
and the length of each meridian is equal to the length of the diameter
of the globe but their lengths between the parallels go on _ towards
the poles.
d. In Cylindrical Equi -Distant Projection Parallels and meridians are _
lines and the meridians intersect the parall els at angles.
e. In Conical Two Standard Parallel the pole is represented by an .
3. Multiple choice question
a. The equal area map projection
i. aims to preserve the area relationships of all parts of the globe and
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28 iii. preserves angles around points, and shape of small areas.
b. The globe is divided into various segments
i. by rivers and mountains.
ii. by the lines of latitude and longitude.
iii. by roads and rail lines.
c. The network of parallels and meridians is called
i. projection.
ii. drainage network.
iii. graticule.
d. In Zenithal Polar Equal Area Projection
i. The meridians intersect the parallels at right angles.
ii. The scale along the meridians is true.
iii. a 2 dimensional plane of projection touches the generati ng globe at
either of the poles.
e. In Conical one standard parallel
i. the scale is correct along the standard parallel but very large along
other parallels.
ii. the parallel are concentric circles.
iii. the scale along the parallels increases away from the centre of the
projection.
4. Answers the following Questions
1. What is a map projection?
2. What is the need of map projection?
3. What do you understand by classification and suitability of Map
Projections?
4. What are the properties of Zenithal Polar Equi -Distant Projection?
State its advantages.
5. State the properties of Conical Two Standard Parallel and its
disadvantages.
6. Compare the advantages and disadvantages of Cylindrical equal area
and Cylindrical equidistant projections.
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29 7. Write short notes on:
a. Equal area map projection
b. Confo rmal map projections
c. Mercator projection
d. Equidistant map projection
1.12. ANSWERS TO THE SELF LEARNING
QUESTIONS
1.a. true
1.b. false, To portray a curved plane on a 2 dimensional plane or a map
we need to construct a "projection" to alter the curved space and make
it flat.
1.c. false, The earth's surface projected on a map wrapped around the
globe as a cylinder produces the cylindrical map projection.
1.d. true
1.e. false, Conical one standard parallel projection is commonly used for
showing areas of mid-latitudes with limited latitud inal and larger
longitudinal extent.
2.a. Conical Two Standard Parallel
2.b. Cylindrical Equal Area
2.c. meridians , decreasing
2.d. straight, right
2.e. arc
3.a. i.
3.b. ii
3.c. iii
3.d. iii
3.e. i.
1.13. TECHNICAL WORDS
1. Projection : a systematic presentation of intersecting coordinate lines
on a flat surface upon which features from a curved surface (as of
the earth or the celestial sphere) may be mapped such as an equal -area
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30 2. Graticule : a network of lines representing meridians and parallels,
on which a map or plan can be represented.
3. Globe - it is a three -dimensional, spherical, scale model of Earth
1.14. TASK
1. In a chart define map projection and write down the properties of
Zenithal polar equal area, Zenithal equidistant, Conical one standard
parallel, Conical two standard parallel, Cylindrical eq ual area and
Cylindrical equidistant projections.
1.15. REFERENCES FOR FURTHER STUDY
 Kellaway, G.P., 1979: Map Projections, B.I. Publications, New Delhi
 Misra, R.P. and Ramesh, A. 1986: Fundamentals of Cartography,
Macmillan, New Delhi
 Monkhouse, F.J. and Wilki nson, H.R. 1980: Maps and Diagrams,
B.I.Publications Private Limited, New Delhi. 36
 Robinson, A.H., Morrison, J.L., Muehrcke, P.C., Kimerling, A.J. and
Guptill, S.C. 1995: Elements of Cartography, John Wiley and Sons,
New York.
 Singh, R.L. and Singh, R.P.B . 1992: Elements of practical Geography.
 Steers, J.A.1954: An Introduction to the Study of Map Projections,
University of London Press, London.
 Oxford dictionary

❖❖❖❖

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31 2
MAP -BASIC
After going through this chapter you will be able to understand the
following features:
Unit Structure
2.1. Objectives
2.2. Introduction
2.3. Subject discussion
2.4. Concept of Map
2.5. Basic components of the map
2.6. Types of maps
2.7. Methods of enlargement and reduction of maps
2.8. Location
2.8.1.Four -figure grid references
2.8.2.Six-figure grid references
2.9. Distance
2.10. Directions
2.11. Area calculation (graphical and strip method)
2.12. Summary
2.13. Check your Progress/Exercise
2.14. Answers to the self-learning questions
2.15. Technical words and their meaning
2.16. Task
2.17. Refere nces for further study
2.1 OBJECTIVES
By the end of this unit you will be able to:
 Understand the concept of map
 Learn basic components of map munotes.in

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32  Discuss types of maps
 Evaluate methods of enlargement and reduction of maps
 Learn location of map
 Learn distance of map
 Learn directions of map
 Learn area calculation (graphical and strip method) of map
2.2 INTRODUCTION
In this unit named Map -Basic, we will study about the concept and the
distinguishing characteristics of Maps. There will be a discussion on basic
components of map and the types. Methods of enlargement and reduction
of maps is very important. We will learn that in this unit. We will also
learn location, distance and directions of map. Area calculation of map
both graphical and strip method will be discussed in the latter part of this
unit.
2.3 SUBJECT -DISCUSSION
Map is a two-dimensional form of the three dimensional earth that
represent geography and culture. Since time immemorial people have been
making pictures of places that were different than maps today. The
earliest maps were carved on rocks. Those illustrations show beliefs and
rituals connected with wider cosmologies. Down the ages, with the
nations’ expansion,n the need for maps became more evident. People need
maps now to make a very large area look small and understandable.
Hence, maps are the primary tools by which spatial relationships are
visualized. SoMaps are considered as important documents. There are
several key elements that should be included each time a map is created in
order to help the reader to understand the communications of that map and
to document the source of the geographic information used.
Maps have important parts and the acronym DOGSTAILS makes it easy
to remember. These are described below.
 Date or D states When the map was made
 Orientation or O states the Directions (north arrow)
 Grid or G Locates places on the map
 Scale, S, states what the map distance is
 Title or T describes What, where, and when
 Author or A states Who made the map
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33  Legend or L describes what the symbols mean
 Sources or S states Basis for map information
2.4 CONCEPT OF MAP
A Map is the representation of the earth’s pattern as a whole or a part of
it, or the heaven on a plane surface with conventional signs, drawn to a
scale and p rojection so that each and every point on its corresponds to the
actual terrestrial or celestial position. The
work of a map is to illustrate specific and detailed feature of a particular
area, there are many kinds of map; static, two- dimensional, three -
dimensional, dynamic and even interactive. Maps attempt to represent
various things like political boundaries, physical features, roads,
topography, population, climates, natural resources and economic
activities.
2.5 BASIC COMPONENTS OF MAP
Maps may contain a variety of elements or components they are as
follows
1) Base Map
2) Projection
3) Title
4) Scale
5) Compass rose - Direction
6) Conventional signs & symbols
7) Lettering in the map
8) Legend (or key)
9) Date
Without these five components, the map would not be a productive map
for use.
1) Base Map - Base map is the map drawn accurately & is obtained
from the authentic source. e.g. Govt. publication etc.
2) Projection - There are many different types of projections. Each
projection has specific characteristics & hence we select base map
drawn on suitable projection as per our requirement. e.g. equal area
projection is used to show distribution of geographical features.
3) Title – The title of a map tells the reader what they are looking at. It
could be a simple name of a country. The title sho uld clearly explain
what the cartographer is trying to show.
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34 4) Scale – the scale on the map allows the reader to see the size and the
distance of the features on the map.
5) Compass rose-Direction – the compass rose on the map orients the
reader with the cardi nal directions of the map. North direction is
marked on the map. Cardinal directions are East, West, North, South.
6) Conventional signs & symbols - Map is a generalized picture of the
earth’s surface. Signs & symbols are used to represent distribution in
symbolic form e.g. church or CG means camping ground etc. signs &
symbols help us to under geographical features.
7) Lettering in the map - Lettering help us in reading details given in
the map. Large size old letters are used to represent title or large areas
like continents or oceans. Small size letters are used for small
villages.
Upright letters are used for land features and slant letters are used for
water bodies like rivers, sea or oceans.
8) Legend – a map legend, or key, helps the reader interpret what is
on the map. The key should explain every feature or symbol on the
map.
9) Date – every map must have a date. This tells the reader when the
map was created. Without a date the reader would not know the
relevance of the map.
There are various ways by which the earth is mapped.
1) By actual survey with the help of the instruments like chain,
prismatic compass, plane table, theodolite etc.
2) By photographs.
3) By freehand sketches and diagrams.
4) By computer.
5) By satellite and remote sensing methods.
2.6 TYPES OF MAPS
A map is the representation of the earth surface or a part of it or some
other celestial body such as sun, moon, stars or planets on a flat surface
i.e. a plane surface. The representation is drawn to a specific scale and
map projection and shows distinctive aspect s of the surface such as relief
features, routes, settlements etc.
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35 2.6.1 Classification of Maps based on scale
a) Cadastral Maps – Cadastral maps are drawn to register the ownership
of landed property by demarcating the boundaries of fields and
buildings etc. they are prepared specially by government to realize
revenue and tax.
b) Topographical Maps – Topographical maps are prepared on a large
scale. They show general surface features detail comprising bo th
natural landscape and cultural landscape. They do not show plot or
boundaries of the building but topographic forms like relief and
drainage, swamp and forests, villages and towns and means of
communication on them. In India 1: 50,000 scale maps are generally
prepared.
c) Wall maps – They are used in classrooms. In these maps, the world as
a whole or in hemisphere is distinctly represented. They may also be
prepared for a continent or country, large or small, according to need.
d) Chorographical or atlas maps – These maps are drawn on a very
small scale and give more or less highly generalized picture
regarding the physical, climate and economic conditions of different
regions of the earth. These maps show only important peaks,
important rivers, chief towns, railway lines, etc.
2.6.2 Maps based on purpose or contents
a) Astronomical Maps – These maps shows heavenly body or heavenly
feature.
b) Geological Maps – They show the rocks that from the crust of the
earth and their mode of occurrence and their deposition. A correlat ion
of these maps with the corresponding relief maps reveals the causes
and evolution of landforms.
c) Orographic or Relief Maps – Maps showing the surface forms is
termed as ore -graphic or relief maps. They show the bulges and
depressions found over the surf ace. The level of land, its slope and
drainage are well marked on it.
d) Weather and climate Maps – They show the average condition of
temperature, pressure, wind and precipitation over a short period,
which range from a day to a season. Map showing daily wea ther
conditions are termed as daily weather maps while those showing the
average of weather conditions over 10 years or more are called
climatic maps.
e) Political Maps – Show boundaries between different states or
boundaries between different political units within a country.
f) Historical Maps – Maps showing historical events are called
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36 g) Social Maps – Social organism tribes and races their languages,
religions, etc. are depicted on social maps.
h) Population Maps – It denotes distribution of man over an area.
i) Economic Maps – Maps displaying the distribution of important
centers of agricultural, minerals and industrial products and its
linkages with various means of communication may be termed as
economic map.
j) Military Maps – These maps records strat egic point, routes, battle
plans, etc.
k) Land utilization Maps – They exhibit the nature and character of
land use.
2.7 METHODS OF ENLARGEMENT AND REDUCTION
OF MAP
The significance of the scale of any map is immediately recognized when
particular map is to be enlarged or reduce. A small -scale map cannot
possibly show and roads can only be shown in a much generalized way
which means that these features cannot be measured to scale. A small -
scale map can be enlarged to show more details and conversely a large
scale map can be reduced.
Nowadays maps can be, enlarged or reduce in a number of ways, be its
graphical or instrumental one common method of enlarging and reducing
map is the square method.
2.7.1 Enlarging map
While enlarging any map to a given size, the following st eps should be
followed.
 Measure the length and width of the map.
 Multiply the length and width by 2 or 4 respectively if intend to enlarge
the map to twice or thrice its original size.
For e.g.: - If the length and width of a map are 5cm and 3cm respectivel y
such a map would measure 10cm by 6cm if enlarge to twice its size and
20cm by 12cm if enlarged 4 times its size and so on.
 Having enlarged the original map it is equally obvious that the scale
would change therefore if a map has a scale of 1:60000 the sc ale of
the map changes to 1:30000 if the size of the map has been enlarged to
four times its original size.
 The feature to be shown on the enlarged map should also be
proportional to the required size of the map.
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37  Once it is finished drawing the enlarged ma p write its title and the
new horizontal scale.
Q.1 Enlarge the given map of Dharwad in the proportion of 1:2

Answer -
1) Draw grid of 1cm ƒ 1 cm on the map.
A B C D E
2) Give number to rows & alphabets to columns.
3) Our enlargement ratio is 1 :2 & so draw a grid of 2cm ƒ 2cm on the
plain paper give numbers & alphabets as per the original diagram.
4) Now carefully transfer details on the new enlarged grid as per the
original grid on the map of Dharwad carefully transfer details of each
square - one by one.
5) Measure length of the graphical scale. It is 1cm to 25km our
enlargement ratio is 1:2 SD draw a line of 2cm on the enlarged map &
write some numbers i.e. zero (0) and 25 kms.
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38
6) Give title draw north to the enlarged map.
2.7.2 Reducing map
In reducing any map to given size the following steps to be followed.
• Measure the length and width of the map.
• Divide the length and width by 2 or 4 if you are asked to reduce the
map to half or a fourth of its original size.
For e.g.: - If the length and width of a map are 24cm and 20cm respectively
such a map should measure 12cm by 10cm if reduce to half of its size
and so on.
• Having reduced the original map, it is obvious that the scale would
equally change. Therefore if a map has a scale of 1:50000, the scale of
the m ap changes to 1:1,00,000 if the size has been reduced to half and
1:2,00,000 if the size of the map has been reduced to a fourth of its
original size.
• The feature to be shown on the reduced map should also be
proportional to the required size of the map.
• Once we have finished drawing the reduced map write its title and new
horizontal scale






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39 Q.1 Reduction the map of Brazil in the proportion of 2:1.


Answer -
1) As the map is large we can draw grid of 2cm ƒ 2cm on the map. (For
small maps use grid of 1cm ƒ 1cm).
2) Give numbers to rows & alphabets to columns.
3) Our reduction ratio is 2:1 & SD we can prepare grid of 1cm ƒ
1cm for drawing reduced map.


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40 4) Now concentrate on the single square of the original map & draw
carefully similar shape in the reduced grid. It is easy to complete entire
map.
5) For drawing scale of the map, measure length of scale on the original
map. It is 2.2cm our ratio is 2:1 & hence we will draw line of 1.1cm on
the reduced map. The value of 800km remains same.

2.8 LOCATIONS ON MAPS
Grid lines on maps define the coordinate system. These are numbered to
provide a unique reference to features. Grid references define locations
on maps. The grid numbers on the east-west (horizontal) axis are called
Eastings, and the grid numbers on the north -south (vertical) axis are
called Northings. Numerical grid references consist of an even number of
digits. Eastings are written before Northings. So in a 6 digit grid reference
123456, the Easting component is 123 and the Northing component is 456.
There are var ied Grid systems. But the most common is a square grid with
grid lines intersecting each other at right angles and numbered
sequentially from the origin at the bottom left of the map.
2.8.1 Four -figure grid references
When giving a four-figure grid reference, you should always give the
eastings number first and the northings number second, just like in
graph where we give the x coordinate first followed by the y.

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41

Fig: Four -figure grid references
For example, the number 2 in the diagram below is square 19 acros s and
square 45 up and therefore, the four-figure grid reference is ‘1945’, the
number 1 in the diagram is 18 45, the number 3 in the diagram is 18 44
and the number is 19 44.

Six-figure grid references
To get the six -figure grid reference, we have to im agine that the four-
figure square is further divided up into tenths. This is explained in the
example below. The grey box is in the four-figure grid reference square
‘18 44’, but more accurately it is 7 tenths across and 8 tenths up within
that larger grid square, therefore the six- figure map reference is ‘187
448’.

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42

The shapes on the diagram above have the following six-figure grid
references:
Grey square – 187 448 and Red dot – 185 443
There are a few points that we should remember regarding grid refer ence.
Four figure grid references are very useful but it has a major weakness.
They are not very accurate because all objects in the same grid square
have the same four figure grid reference even though they may be
hundreds of meters apart. Hence for great er accuracy a six figure grid
reference is used. A six figure grid reference does not only indicate the
grid square an object is located in. It also tells us the exact point within the
grid square where the object is found. Therefore, objects located in th e
same grid square will have the same four figure grid reference, but
different six -figure grid references.
2.9 DISTANCE ON THE MAP
Maps are not only useful for directions, but can also help one determine
the distance between two or more places. Thus people use a map scale to
measure distance between cities and other places on a map. How we can
measure distances on a map is discussed below.
• At first one should find the scale for the map one is going to use.
One can use a ruler bar scale or a written scale, in words or numbers. At
the bottom of each map there is a scale that indicates the distance on the
map. While measuring a distance on the map, one must compare it to the
scale. This will instantly tell him the real world distance.
• A ruler should be used to measure the distance between the two
places. A straight line distances may be easily measured on a map with
a ruler. However, when using this technique above, a pencil, fingers or a
twig may be considered as a tool to get a distance and compare it to the
map scale. But if the line is curved, one should use a string to determine
the distance and then measure the string.
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43 • If the scale is a representative fraction (and looks like 1/100,000 or
1:100,000), multiply the distance of the ruler by the denominator , giving
distance in the ruler units.
Examples:
8.5cm measured on a 1: 25 000 scale Multiply distance by scale
8.5cm x 25,000 =212,500 cm
Convert to meters 212,500 / 100 = 2,125 m
Convert to km:
2,125 / 1,000 = 2.125 km
• If the scale is a word statement (i.e. "One centimeter equals one
kilometer") then determine the distance.
• For a graphic scale, one needs to measure the graphic and divide
the scale into the measured units on the ruler.
• One should convert the units of measurement into the most convenient
units for him such as conversion of 63,360 inches to one mile.
• A graphic scale will change with the reduction or enlargement but the
other scales become wrong. So one should watch out for maps that
have been reproduced and have had their scale changed.
• Remem ber that the grid lines on a 1:25 000 scale map are 1km apart.
A quick way of estimating distance is to count each square you cross
in a straight line. If going diagonally the distance across the grid
square is about 1½km.
• There are other ways to measure m ap distance using a romer or map
measurer. A romer is a ruler that is scaled with a specific map
scale. Instead of reading in cm and converting, one can read the
distance directly. But the romer must have the same scale as the map is
being used. A map meas urer is a mechanical or electronic tool with
a small wheel that you run over the map. You can then read off the
converted distance. Again, check the manual to make sure you are
using the correct scale conversions.
2.10 DIRECTION ON MAPS
Similar to distance, dir ection is difficult to measure on maps due to the
distortion produced by projection systems. Nevertheless this distortion is
somewhat small on maps having scales larger than 1:125,000. Direction is
usually measured relative to the location of North or South Pole.
Directions determined from these locations are said to be relative to
True North or True South.
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44 2.10.1 Direction and Bearings
Directions and bearings are terms we use to communicate where one
location is relative to another location. Directions uses the four points
of the compass i.e. North, South, East and West, and bearings uses a
system of 360 degrees and a protractor.
We are able to communicate where one location is relative to another
with the help of these two approaches. For example, Mumbai is south of
Ahmedabad and Alibag is south of Mumbai.
There are four points of the compass, North, South, East and West.
Importantly, North does not mean up in the sky, but means the direction
that a compass points to as magnetic north (which is a location near th e
North Pole). Based on this being north, the opposite is south (hence the
South Pole), and east and west are directions that move us around the
earth parallel to the poles.
As we know that there are eight major directions that we commonly use.
The first four, North, South, East and West are called the cardinal
directions. Another four equal divisions such as Northeast, Southeast,
Southwest and Northwest, are called Primary Inter Cardinal directions. A
direction between two points, for example a direction halfway between
North and East, is called North East. Similarly, a direction halfway
between West and South would be called South West. Occasionally,
sixteen directions are used such as WSW = West -southwest
So we can see there are sixteen divisions. With so many directions, it turns
out to be utter confusing. Hence, we use numbers called bearings. There
are 360° of bearings. The number would have been more had we used
decimals. So commonly we use only 360.
All of these bearings and directions appear on magne tic compasses, which
are used to figure out directions and calculate exact bearings. Many people
use GPS systems instead of compasses today. But a simple protractor can
be used to calculate bearings on a diagram or map.
2.10.2 Bearings
• Definition:
Bearing is a ho rizontal arc or angle measured from a north reference line,
in a clockwise direction, to a point of interest some distance away from
the point of measurement.
Bearings are a more precise way to indicate direction. We use a protractor
to measure it. We know that a circle has 360 degrees, with 180 degrees in
each half of the circle. A bearing will be a number, between 0 and 360
degrees, which represents the direction that one location is when viewed
from a starting location.
The most important part regarding bearings is that everyone should
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45 because one person may think it is 180 degrees, when it may appear as
360 degrees to another or something different entirely.
2.10.3 How to see bearings
Bearin gs are always calculated based on north being zero degrees, and
degrees are then counted moving clockwise around the circle from there.
Bearings can be seen using a protractor. The following depicts steps
involved in seeing a bearing between two points:
a. Draw a line between the two points which will be long enough to see
using your protractor.
b. Place the protractor on the map, with 0 degrees pointing north, and the
centre of the protractor on the starting location.
c. Read on the protractor the degrees that the line between the two
points follows. If your protractor only has 180 degrees, where the
bearing is greater than 180 degrees, you may need to measure the
angle from 360 to your line, and then subtract that from 360 degrees
in order to calculate the bearing.
2.10.4 Common errors
i. A common error with directions is getting the north, south, east and
west labels in the wrong points on the compass.
ii. Not placing the protractor on the starting point for determining the
bearing of the second point.
iii. Not placing the protractor with zero pointing north as indicated by
the orientation on the map.
iv. Incorrectly calculating a bearing when it is greater than 180 degrees. If
the direction is between south and north on the western side, the
bearing must be greater than 180 degrees and less than 360 degrees.
Location, Distance & Direction -
Q.1 Study the following map and answer the following questions.
1) Identify the type of scale given in the map.
Ans - Linear or Graphical scale is given in this map.
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46 2) Convert the given scale into R.F. Ans - Let us redraw scale.

This is linear scale. In this scale length of line is 4cm and
measurement of distance on the ground is 200m.

Hence 4cm to 200 m or 1cm to 50 m (200 ÷ 4 = 50)

Let us prepare simple table to convert 50m into cm

K = Kilometer, H = Hectometer, D = Decameter, M = Meter D =
Decimeter, C = Centimeter, M = Milimter
You can remember all these in the form of simple sentence. Kind Hearted
Daddy Mummy Didi Call Me
OR
Khoi Hui Duniya Me Dusara Kaun Mera
KeesF& n g³eer ogefve³ee ceW ogmeje keÀewve cesje.
K H D M D C M


Verbal scale - 1cm to 50m.
In order to prepare R.F. or Representative Fraction (R.F) it is necessary
that both numbers 1(cm) and 50(m) must be in the same unit. It is
necessary to convert 50m into cm.
K H D M D C M
Verbel Scale = 1cm to 50m
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47 Consider following number 50, 50., 50.0 all three numbers are same.
Complete numbers. So we can give dot (decimal point) after 50.D and this
dot represent meters. In our table line to the right side of the words (K,
H, D , M, D, C, M) is the decimal line for that word.
Put number 50m in the table.
K H D M D C M
5 0

We want to convert 50m into centimeters. Decimal line for centimeters is
to the right side of word ‘C’.
Put decimal point on the line.
K H D M D C M
5 0
Now cancel decimal point of meter and put zero in the ‘D’ and ‘C’
columns.
K H D M D C M

5 0 ƒ 0 0

Hence 50m = 5000cm. Hence our scale is 1cm to 5000cm
so

3) State the direction of ‘B’ from ‘A’ and direction of ‘A’ from ‘B’.
Answer - Direction

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48 4) Measure the straight line distance between ‘A’ and ‘B’.
Answer - Measure distance between ‘A’ and ‘B’ points on the map it is
7.5cm.
Our scale is 1cm to 50m.
Hence 7.5cm are equivalent to 7.5 ƒ 50 = 375.0 m. Hence distance
between ‘A’ and ‘B’ is 375m.
5) Measure distance between ‘A’ & ‘B’ along the railway track or
find out the length of railway route represented in the map.
Answer - Use thread to measure distance between ‘A’ & ‘B’ points along
the railway route keep thread attached to railway line & turn it as railway
route turns or bend. This distance is 11.0 cm & so as per scale 1cm to
50m. 11.0cm are 11 ƒ 50 = 550 m. Hence the length of railway route is
550m.
6) What is the height of point ‘D’?
Answer - It is about 70m. (To find out height of point ‘D’ give values to
all unnumbered contours.)
7) Find out the bearing of ‘C’ from ‘D’.
Answer - Draw north direction at ‘D’ by drawing line parallel to north at
‘D’.
Now measure angle of ‘C’ from north direction in the clockwise
direction.

8) Find out total area covered by the map.
Ans. Area = Length x Width
= 9.5cm x 6.0cm
(Rectangular frame of map)

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49 Scale is 1cm to 50m.
So 9.5cm = 9.5 x 50 = 475.0M & 6.0cm = 6.0 x 50 = 300.0 m
Hence area is 475 x 300 = 142,500 sq.m
Exercise -
Answer questions related to map no. 2, 3 & 4. With reference to the maps
given below.
Map 2

Map 3

Map 4


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50 Map 2 Questions -
1) Measure the length of railway route.
2) State the direction of ‘A’ from ‘C’ and ‘D’.
3) State the bearings of ‘A’, ‘C’ and ‘D’ from ‘E’.
4) State the maximum height represented in the map.
5) State the contour interval (Ans - 300m - 200m = 100m)
6) Find out total area covered by the map.
7) Convert scale of the map into R.F. & Verbal scale.
Map 3 Questions -
1) Measure the length of main river.
2) State the directions of ‘A’ & ‘B’ from ‘C’ (Please note the direction
of North)
3) State height of point A.
4) Find out straight line distance between A-B, A-C and B - C.
5) Find out bearing of ‘A’ & ‘B’ from ‘C’.
Map 4 Questions -
1) Identify major landform represented in the map (Ans. Sea-cliff in
S.W. corner of the map. Zero m. contour line means sea level)
2) What type of scale is drawn on the map convert it into R.F.
3) State the directions & bearing of ‘B’ & ‘C’ from ‘A’.
4) Use blue colour to represent sea (beyond zero meters) green
between 0 m to 30 m &k yellow from 30 m to 60 m.
Area Calculation (1) Grid Method -
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51 Q.1 Find out area of Shimla. Use grid method.

Answer -
1) Draw grid of 1cm x 1cm on the map of Shmla.
2) Identify f ull squares. Total number of full squares are 5 (Fire).
3) Remaining all squares are half squares. Total number of half
squares are 22 (Twenty Two).
4) Convert half squares into full squares by dividing by 2. Hence
22 ÷ 2 = 11
5) Total number of full squares are 5 + 11 = 16 (sixteen)
6) Scale of the map is 1cm to 16 kms.
7) Using this scale let us calculate are of one square cm. 1cm x 1cm to
16km x 16 km 1sqcm to 256 sq. kms.
8) Total number of squares (1cm x 1cm = 1 sq. cm.) are 16 = 16 sq.
cms.
∴ 1sq cm to 256 sq.kms .
∴ 16 sq.cm to 4095 sq kms.
Hence are of Shimla by grid method is 4096 sq. kms.
2.11 AREA CALCULATION ON MAP
2.11.1 Area calculation on map by square method
To calculate the area on a map we should follow the steps below:
Step 1: Work out the area of one grid square on the map.
For example:
If the Scale of the map is 1:50 000, then each cm represents 0.5km
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52 Length: 2cm x 0.5km = 1.0km
Width: 2cm X 0.5 km = 1.0km
Therefore area of One Grid Square = 1.0km x 1.0km = 1.0 sq. km
Step 2: Determine the number of squares that the object occupies. Let us
consider the area to be calculated occupies a total of about
0.5 of a grid square.
Step 3: Multiply the number of grid squares that the object occupies by
the area of one grid square.
Hence, 0.5 of a square x 1.0 sq. km = 0.5 sq. km is the area
2.11.2 Example of Area calculation square method
Area Calculation (1) Grid Method -

Q.1 Find out area of Shimla. Use grid method.



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53 Answer -
1) Draw grid of 1cm x 1cm on the map of Shmla.
2) Identify full squares. Total number of full squares are 5 (Fire).
3) Remaining all squares are half squares. Total number of half
squares are 22 (Twenty Two).
4) Convert half squares into full squares by dividing by 2. Hence
22 ÷ 2 = 11
5) Total number of full squares are 5 + 11 = 16 (sixteen)
6) Scale of the map is 1cm to 16 kms.
7) Using this scale let us calculate are of one square cm. 1cm x 1cm to
16km x 16 km 1sqcm to 256 sq. kms.
8) Total number of squares (1cm x 1cm = 1 sq. cm.) are 16 = 16 sq.
cms.
∴ 1sq cm to 256 sq.kms.
∴ 16 sq.cm to 4095 sq kms.
Hence are of Shimla by grid method is 4096 sq. kms.
2.11.3 Area calculation on map by strip method
❖ Example
• Calculate the area of the given map in sq. mts with the help of strip
method.
Area calculation (2) Strip Method -
Q.1 Find out area of Kully by strip method.


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54 Answer -
1) Draw grid of 1cm width on the map Kullu.

2) Draw Give & take lines for each strip.
Give & take lines are small vertial lines. These are drawn at the Western
& Eastern border of map area for each strip. These lines are used to
convert irregular shape of the count ry / area into regular shape (Rectangle)
so the measurement of area becomes easy.
3) Give & take lines are drawn vertically (i.e. Pergendicular to the
horizontal lines) These lines are drawn with proper judgement that the
portion of map included in the rectan gle and excluded from rectangle are
almost same. Hence these lines are known as Give & take lines. Consider
following examples.
A)

B)



C)




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55 A) Wrong - Extra area is included.
B) Wrong - More area is excluded.
C) Correct Method - Area included & area excluded are same.
4) Give numbers to all strips as S-1, S-2….
5) Measures length of all strips.
S1 = 0.7cm, S 2 = 2.2cm, S 3 = 4.0cm S4 = 4.1cm, S 5 = 3.0cm, S 6 = 1.9cm
S7 = 1.6cm
7) Find out total length of all strips.
Total length =
S1 + S2 + S3 + S4 + S5 + S6 + S7
= 0.7 + 2.2 + 4.0 + 4.1+ 3.0 +1.9 +1.6
Total length = 17.5cm
8) Width of each strip is 1cm.
9) Total area = Total length x Width (1cm)
= 17.5cm x 1cm
= 17.5cm
10) Scale of the map is 1cm to 16 kms 11)Find out area of 1sq. cms
= length x width
= 1cm x 1cm to 16 kms x 16 kms 1 sq.cm to 256 sq. kms.
12)1 sq. cm to 256 sq. kms.
∴ 17.5 sq.cm to 4480 sq.kms. Area of Kullu is 4480 sq.kms.
2.12 SUMMARY:
After going through this unit we may conclude that Map is a diagrammatic
representation of an area of land or sea showing physical featu res, cities,
roads, etc. It is a form of human communication that represents geography
and culture. Moreover to show distribution of resources and bring out
relationship amongst geographic elements map are needed. These are also
used as tools for planning urban development along with selection of areas
for the construction of dams and highways. There are four parts of a
map such as Title, Scale, Compass Rose and Key. Title, usually found on
the top or bottom of the map, tells us what the map is. Scale state s the
relationship between distance on a map and actual distance on the earth.
Scale may be represented by words (e.g., “one inch equals one mile”), a
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56 distance between cities and other places on a map. Compass Rose is an
object that appears on maps to identify four main directions: North, South,
East and West. Key is found on the bottom of the map. The map key tells
us what the symbols on the map stand for. Symbols are small pictures
on the map used for representing real things on our Earth like mountains,
hills, and valleys etc.
Maps can be classified on the basis of scale and contents. Cadastral Maps,
Topographical Maps , Wall maps Chorographical or atlas maps
Astronomical Maps Geologi cal Maps Orographic or Relief Maps, Weather
and climate Maps, Political Maps, Historical Maps Social Maps,
Population Maps, Economic Maps, Military Maps and Land utilization
Maps are the names of different types of maps. At present maps can be
enlarged or reduced in a many ways. It may be graphical or instrumental.
One common method of enlarging and reducing map is the square method.
Locations on maps may be done by Four -figure and six figure grid
references. Scale on map is use to measure distance between cities and
other places on a map. There are many ways by which distances on a map
is measured. Similar to distance, direction is difficult to measure on
maps. Bearings are a more precise way to indicate direction. We use a
protractor to measure it. Area is calculated on map by square method and
strip method.
2.13 CHECK YOUR PROGRESS/ EXERCISE
1. True false
a. Map is a two -dimensional form of the three dimensional earth that
represent geography and culture.
b. The scale of a map tells the reader what they are looking at.
c. A map legend, or key, helps the reader interpret what is on the map.
d. While finding the location of any place on a map at first we should
measure the length and width of the map.
e. To get the six -figure grid reference, we have to imagine that the
four-figure square is further divided up into tenths.
2. Fill in the blanks
a. The _on the map orients the reader with the cardinal directions, East,
West, North, and South, of the map.
b. _ maps are drawn to register the ownership of landed property by
demarcating the boundaries of fields and buildings etc.
c. -- maps, where the world as a whole or in hemisphere is distinctly
represented, are used in classrooms.
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57 e. A scale will change with the reduction or enlargement but the other
scales become wrong ---
3. Multiple choice question
a. Every map must have a date because
i. it allows the reader to see the size and the distance of the features
on the map.
ii. this tells the reader when the map was created and without it the
reader would not know the relevance of the map.
iii. it clearly explains what the map maker (cartographer) is trying to
show.
b. There are various ways by which the earth is mapped such as
i. by actual survey with the help of the instruments like chain, prismatic
compass, plane table, theodolite etc., by photographs, by freehand
sketches and diagrams and by computer.
ii. by multiplying the length and width of the area to be mapped by 2
or 4 respectively if intend to show the area to twice or thrice its
original size.
iii. By measuring the Bea rings of the area to indicate direction with a
protractor.
c. A Social Map
i. denotes distribution of man over an area.
ii. displays the distribution of important centres of agricultural, minerals
and industrial products and its linkages with various means of
commun ication.
iii. denotes Social organism tribes and races their languages, religions,
etc. on maps.
4. Answers the following Questions
1. What are the Basic components of map?
2. What is a map? Elaborate your answer stating different types of maps.
3. State the methods of enlargement and reduction of maps
4. How will you find the location of a place on map?
5. State how to calculate Area on map.
6. Write short notes on:
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58 b. Six-figure grid references
c. Distanceon map
d. Directions on map
2.14 ANSWERS TO THE SELF LEARNING QUESTIONS
1.a. true
1.b. false, The title of a map tells the reader what they are looking at.
1.c. true
1.d. false, While enlarging or reducing any map to a given size at first
we should measure the length and width of the map.
1.e. true
2.a. Compass rose
2.b. Cadastral
2.c. Wall
2.d. nature and character
2.e. graphic 3.a.ii.
3.b.i.
3.c.iii.
2.15 TECHNICAL WORDS:
1. Map -A map is a visual representation of an entire area or a part
of an area, typically represented on a flat surface. There are many
kinds of maps; static, two-dimensional, three - dimensional, dynamic
and even interactive. Maps attempt to represent various things, like
political boundaries, physical features, roads, topography,
population, climates, natural resources and economic activities.
2. Grid reference -a map reference indicating a location in terms of a
series of vertical and horizontal grid lines identified by numbers or
letters.
3. Four figure grid -A four figure grid reference points you towards a
particular square on a map. On all OS maps these squares represent
one square kilometre. All maps will have lines numbered around
the edge
4. Six figure grid - Numerical grid references consist of an even
number of digits. Eastings are written before Northings. Thus in a 6
digit grid reference 123456, the Easting component is 123 and the
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59
5. Map scale - it refers to the relationship (or ratio) between distance
on a map and the corresponding distance on the ground. For
example, on a 1:100000 scale map, 1cm on the map equals 1km on
the ground.
6. Cartographer - map maker
2.16 TASK
1. Convert Representative Fraction into graphical form in cms. to
kms. R.F is 1:7820000
2. Convert Representative Fraction into vertical scale in cms. to
kms. R.F is 1:2570000
3. Convert vertical scale into Representative Fraction when vertical
scale is 2 cm: 5 kms.
2.17 REFERE NCES FOR FURTHER STUDY
 Gupta K. K and Tyagi V. C., 1992: Working with Maps, Survey of
India, DST, New Delhi.
 Singh R. L. and Singh R. P. B., 1999: Elements of Practical
Geography, Kalyani Publishers
 Sarkar A.K Practical Geography: A Systematic Approach, Oriental
Longman, Calcutta, 1997.
 Oxford dictionary
❖❖❖❖ 

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60 3
SURVEY OF INDIA TOPOSHEETS
After going through this chapter, you will be able to understand the
following features:
3.1. Objectives
3.2. Introduction
3.3. Subject discussion
3.4. Definition of topographical map
3.5. Methods of showing relief and landforms
3.6. Topographical map index
3.7. Colour scheme used in topographical maps
3.8. Interpretation of map: a) S.O.I. Topographical Maps
3.9. Conventional signs and symbols
3.10. Utility of topographical maps in geographical analysis
3.11. Summary
3.12. Check your Progress/Exercise
3.13. Answers to the self-learning questions
3.14. Technical words and their meaning
3.15. Task
3.16. References for further study
3.1. OBJECTIVES
By the end of this unit you will be able to:
 Understand the Definition of a topographical map
 Learn Methods of showing relief and landforms
 Discuss Topographical map index
 Learn Understand Colour, skim used in topographical maps
 Understand Conventional signs and symbols
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61 3.2 INTRODUCTION
In this unit, we will study topographical maps along with the methods of
showing relief and landforms. After that there, will be a discussion on
Topographical map index. We will also study colour, skim used in
topographical maps. Conventional signs and symbols and utility of
topographical maps will also be discussed in the latter part of this unit.
3.3. SUBJECT -DISCUSSION
The topographical maps represent the Earth’s features accurately and to
scale on a two dimensional surface. It is characterized by large -scale
detailed and accurate illustration of man-made as well as natural features
on the earth surface such as roads, railways, power transmission lines,
contours, elevations, rivers, lakes and geographical names. Hence,
Topographic maps are an excellent planning tool and guide. These maps
give us a variety of information identifying innumerable ground features.
We may group these features into the following categories:
a. Relief : mountains, valleys, slopes, depressions as defined by contours
b. Hydrography : lakes, rivers, streams, swamps, rapids, falls, coastal
flats
c. Vegetation : wooded and cleared areas, vineyards and orchards.
d. Transportation : roads, trails, railways, bridges, airports/airfield,
seaplane anchorages
e. Culture : buildings, urban development, power transmission line,
pipelines, towers
f. Boundaries : international, provincial/territorial, administrative,
recreation al, geographical
g. Toponymy : place names, water feature names, landform names,
boundary names
The map legend gives us a complete list of all features present in the map
along with their corresponding symbols. If we see the map minutely we
will find some in formation along the map borders. These provide valuable
details which in turn help us understand and use a topographic map. We
can determine relative and absolute positions of mapped features from the
geographic graticule and a coordinate grid that the Top ographic maps
usually show.
The most important part lies in the representation of these maps because as
these are two -dimensional representation of the Earth’s three -dimensional
landscape at a given time, are not always entirely up to date.
Topographical maps for territorial coverage of India are prepared and
published by Survey of India. In India topographical maps are available in
two series:
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62 b. International Map Series of World or La carte International Du
Monde (CIM) series.
Topographic maps are based on topographical surveys. Performed at
large scales, these surveys are called topographical in the old sense of
topography, showing a variety of elevations and landforms. This is in
contrast to older cadastral surveys, which primarily show property and
governmental boundaries. The first multi -sheet topographic map series of
an entire country, the Carte géométrique de la France, was completed in
1789. The Great Trigonometric Survey of India, started by the East
India Compa ny in 1802, then taken over by the British Raj after 1857 was
notable as a successful effort on a larger scale and for accurately
determining heights of Himalayan peaks from viewpoints over one
hundred miles distant.
These maps are also prepared on a fairl y large scale. They are based on
precise surveys conducted by the Survey of India, Dehradun. They show
general surface features in detail both natural and cultural. Principal
topographic features depicted on these maps are relief, drainage, swamps
and lakes, forests, villages, towns, means of transport and
communication like roads and railways, and canals. Indian toposheets are
generally prepared on the scale of 1:50,000.
3.4. DEFINITION OF TOPOGRAPHICAL MAP:
In modern mapping, a topographic map is a type of map characterized by
large -scale detail and quantitative representation of relief, usually using
contour lines, but historically using a variety of methods. Traditional
definitions require a topographic map to show both natural and man -made
features. A topogr aphic map is typically published as a map series, made
up of two or more map sheets that combine to form the whole map. A
contour line is a line connecting places of equal elevation.
Natural Resources Canada provides this description of topographic maps:
These maps depict in detail ground relief (landforms and terrain), drainage
(lakes and rivers), forest cover, administrative areas, populated areas,
transportation routes and facilities (including roads and railways), and
other man-made features.
Other auth ors define topographic maps by contrasting them with another
type of map; they are distinguished from smaller -scale "chorographic
maps " that cover large regions, " planmetric maps " that do not show
elevations, and " thematic maps" that focus on specific topics.
However, in the vernacular and day to day world, the representation of
relief (contours) is popularly held to define the genre, such that even
small -scale maps showing relief are commonly (and erroneously, in the
technical sense) called "topographic".
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63 3.5. METHODS OF SHOWING RELIEF AND
LANDFORMS:
Topography is the study of the shape and features of the surface of the
Earth. This field of geoscience and planetary science is concerned with
local detail in general, including not only relief but also natural and
artificial features, and even local history and culture. Mapmakers use
several methods to depict relief of the terrain.
A. Hachures : Hachures are short, broken lines used to show relief.
Hachures are sometimes used with contour lines. They do not represent
exact elevations, but are mainly used to show large, rocky outcrop areas.
Hachures are used extensively on small -scale maps to show mountain
ranges, plateaus, and mountain peaks. Hachures are an older mode of
representing relief. They show orientation of slope,and by their thickness
and overall density they provide a general sense of steepness.
Fig: showing contours
B. Contours : Imaginary lines joining all the points of equal elevation
or altitude above mean sea level. They are also called “level lines”.
Cross -section : A side view of the ground cut vertically along a
straight line. It is also known as a section or profil e. .
A map showing the landform of an area by contours is called a contour
map . The method of showing relief features through contour is very useful
and versatile. The contour lines on a map provide a useful insight into the
topography of an area. Earlier, ground surveys and levelling methods
were used to draw contours on topographical maps. However, the
invention of photography and subsequent use of aerial photography have
replaced the conventional methods of surveying, levelling and mapping.
Henceforth, t hese photographs are used in topographical mapping.
Contours are drawn at different vertical intervals (VI), like 20, 50, 100
metres above the mean sea level. It is known as contour interval. It is
usually constant on a given map. It is generally expressed in metres.
❖ Some basic features of contour lines are as follows:
a. A contour line is drawn to show places of equal heights.
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64 b. Contour lines and their shapes represent the height and slope or
gradient of the landform.
c. Closely spaced contours represent steep slopes while widely spaced
contours represent gentle slope.
d. When two or more contour lines merge with each other, they
represent features of vertical slopes such as cliffs or waterfalls.
e. Two contours of different elevation usually do not cross each
other.
❖ Types of slope -The slopes can broadly be classified into gentle,
steep, concave, convex and irregular or undulating. The contours of
different types of slopes show a distinct spacing pattern.
• Gentle Slope -When the degree or angle of slope of a feature is very
low, the slope will be gentle. The contours representing this type of
slope are far apart.
• Steep Slope -When the degree or angle of slope of a feature is high and
the contours are closely spaced, they indicate steep slope.
• Concave Slope -A slope with a gentle gradient in the lower parts of a
relief feature and steep in its upper parts is called the concave slope.
Contours in this type of slope are widely spaced in the lower parts and
are closely spaced in the upper parts.
• Convex Slope -Unlike concave slope, the convex slope is fairly gentle
in the upper part and steep in the lower part. As a result, the contours
are widely spaced in the upper parts and are closely spaced in the
lower parts.
❖ Types of Landforms:
❖ Conical Hill-Conical hill rises almost uniformly from the surrounding
land. A conical hill with uniform slope and narrow top is represented
by concentric contours spaced almost at regular intervals.
❖ Plateau –Plateau is a widely stretched flat-topped high land, with
relatively steeper slopes, rising abov e the adjoining plain or sea. The
contour lines representing a plateau are normally close spaced at the
margins with the innermost contour showing wide gap between its two
sides.
❖ V-Shaped Valley -A Geomorphic feature lying between two hills or
ridges and fo rmed as result of the lateral erosion by river or a glacier is
called a valley. It resembles the letter ‘V’. A V -shaped valley occurs in
mountainous areas. The lowermost part of V - shaped valley is shown
by the innermost contour line with very small gap between its two
sides and the lows value of the contour is assigned to it. The contour
value increases with uniform intervals for all other contour lines
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❖ U-Shaped Valley -A U -shaped valley is formed by strong lateral
erosion of glaciers at high alti tudes. The flat wide bottom and steep
sides makes it resemble the letter U. The lowermost part of the U -
shaped valley is shown by the innermost contour line with a wide gap
between its two sides. The contour value increases with uniform
intervals for all other contour lines outward.
❖ Gorge -In high altitudes gorges form in the areas where the vertical
erosion by river is more prominent than the lateral erosion. They are
deep and narrow river valleys with very steep sides. A gorge is
represented by very closel y-spaced contour lines on a map with the
innermost contour showing small gap between its two sides.
❖ Spur -A tongue of land projecting from higher ground into the lower
ground is called a spur. It is also represented by V -shaped contours but
in the reverse m anner. The arms of the V point to the higher ground
and the apex of V to the lower ones.
❖ Cliff -Cliff is a very steep or almost perpendicular face of landform.
On a map, a cliff may be identified by the way the contours run very
close to one another, ultima tely merging into one.
❖ Waterfalls andRapids -A sudden and more or less perpendicular
descent of water from a considerable height in the bed of a river is
called a waterfall. Sometimes a waterfall succeeds and proceeds with
cascading stream forming rapids upstream or downstream of a
waterfall. The contours representing a waterfall merge into one another
while crossing a river stream and the rapids are shown by relatively
distant contour lines on a map.
C. Form Lines : Form lines are not measured from any datum plane.
Form lines have no standard elevation and give only a general idea of
relief. Form lines are represented on a map as dashed lines and are never
labelled with representative elevations.
D. Spot Height : The term is generally applied to any item used to mark
a point as an elevation reference. A spot height is an exact point on a map
with an elevation recorded beside it that represents its height above a
given datum. On the top of hills you will see a dot and a number written
beside it. The dot will be inside a small enclosed contour line.
E. Triangulation points : Triangulation pillars are another way of
spotting the top of a mountain on a map. The symbol for a trig point is a
small triangle. Triangulation pillars are used by map makers. They are real
concrete pillars that are placed at particular places which are usually the
tops of hills.
F. Bench mark : Carved or screwed in to thousands of walls around
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66 G. Hillshading is a shaded relief (levels of gray) on a map, just to
indicate relative slopes, mountain ridges, not absolute height. Hillshading
is the process of adding light and dark areas or shading to a map to
highlight the location of hills or mountains. Hillshading uses light and
dark areas to highlight where sunlight would hit and where shadows
would form in the presence of hills and mountains.
H. Hypsometric tints are colors used to indicate elevation, usually
together with contour lines. They can be used to depict ranges of
elevation as bands of color, usually in a graduated scheme, or as a colour
ramp applied to contour lines themselves. A typical scheme progresses
from dark greens for lower elevations up through yellows/browns, and
on to grays and white at the highest elevations. Hypsometric tinting of
maps and globes is often accompanied by a similar method of bathymetric
tinting to convey depth of oceans; lighter shades of blue represent
shallower water such as the continental shelf and darker shades deeper
regions.
3.6. TOPOGRAPHICAL MAP INDEX:
The survey of India has published the following 5 types of topographical
maps. They are as follows:
a. Million maps
The SOI has published topographical maps on the scale of 1:1000000
under the India and Adjacent Series. Each sheet cover 40 at *40 long and
is numbered as 62, 63, 64 etc.
b. Degree or Quarter -Inch series
Each of the map is divided into 16 equal parts, each measuring as 40 at *10
long. Now it has been converted on the scale of 1:250000 on the Metric
scale and is referred as 63A, 63B, 63C etc.
c. Half -degree or half-inch map Series
Each of the degree sheet maps has been divided into 4 equal parts.
Hence, the each sheet is numbered as 63A/NW, 63A/NE, 63A/SW, and
63A/SE.
d. Quarter Degree or One-inch Map series
Each degre e has been divided into 16 equal parts, so the sheet has been
measured as 15’lat and 15’long and is given as 63A/1, 63A/2, 63A/3, etc.
e. Town Guide maps
They are drawn under the scale of 1:25000, and are numbered as
63A/15/NE, 63A/15/NW, 63A/15/SE, etc. It c overs the area of 7.5’lat and
7.5’long.
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67
Inch
sheet
45H/6
NW NE
SW SE 1 5 9 13
2 45H/6 10 14
3 7 11 15
4 8 12 16 Million Sheet :

39 44 53
38 45 54
37 46 53


Degree Sheet



3.7. COLOUR SCHEME USED IN TOPOGRAPHICAL
MAPS:
To facilitate the identification of features on a map, the topographical and
cultural information is usually printed in different colours. These colours
may vary from map to map. On a standard large -scale topographic map,
the colours used and the features each represent are stated under:
Half inch sheet

45H/NW A E I M
B F J N
C G K O
D H L P
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68 a. Black: Indicates cultural (man -made) features such as buildings
and roads, surveyed spot elevations, and all labels.
b. Red-Brown: The colours red and brown are combined to identify
cultural features, all relief features, non -surveyed spot elevations,
and elevation, such as contour lines on red-light readable maps.
c. Blue: Identifies hydrography or water features such as lakes,
swamps, rivers, and drainage.
d. Green: Identifies vegetation with military significance, such as
woods, orchards, and vineyards.
e. Brown: Identifies all relief features and elevation, such as contours
on old er edition maps, and cultivated land on red -light readable
maps.
f. Red: Classifies cultural features, such as populated areas, main
roads, and boundaries, on older maps.
g. Other: Occasionally other colours may be used to show special
information. These are indicated in the marginal information as a
rule.
3.8. INTERPRETATION OF TOPOGRAPHICAL MAPS
The study of topographical maps requires a careful planning, patience and
proper attention. Convectional signs are given on the maps which should
be read carefully. The stud y of topographical maps is classified into three
broad sections.
a. Marginal Information
It is important to find out the marginal information before interpreting the
topographical maps. One must know the following information’s of maps:
1. States and districts to which the map belongs.
2. Latitudes and longitudes, scale, and contour interval.
3. Year of publication, name and number of the map, and its
approximate area.
b. Physiographic Information
These are basic and important information and should be studied under the
following heads:
1. Relief : nature and types of the landform (mountain .plateau or plain),
average height and general slope, important hills, peaks, ridges, valleys
etc. with their heights and their locations.
2. Drainage : important rivers their tributaries and t heir stages; type of
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69 3. Vegetation : areas covered by vegetation, types of forest (protected and
reserved) and other types of trees and their distribution.
c. Cultural Information
Topographical maps bear sufficient information pertaining to cultural
aspects. These include the study of following information:
1. Land use : cultivated land, other uses of land and waste land; means of
irrigation, (canal, well, tank), occupation of people (cultivation,
mining, forestry etc.).
2. Means of Communications : railway, roadway, cart-tracks etc.; postal
and telegraphic offices; Aerodrome, harbours, ports etc.
3. Settlement : Urban Centres, their sites and their sizes; rural settlements,
their types and patterns, archaeological sites and their details.
3.9. CONVENTIONAL SIGNS AND SYMBOLS

Topographical Map Karnataka - 48/N/12 (C-1)
Q.1 With reference to the map (Karnataka - 48/N/12) answer the
following questions.
1) State extent of the map.
Ans - ‘Extent’ refers to the Latitudinal and Longitiudinal extent of the
map.

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70 140
15’
TOPO
graphical Map

140

750

40’E 10’

a) Latitudinal extent = 1
140 10’ N to 14015’ North
b) Longitudinal extent
750 40’ E to 750 45’ East
2) Calculate area represented in the map.
Ans. Formula for the calculation of area Area = Length x Width
Measure length and width of the map Length = 18.0cm
Width = 18.2 cm
Scale of the map is 2cm to 1km.
Let us convert length & width into kms.
∴ 2cm to 1 km
(18/2=9)
∴ 18cm to 9.1 km
Lengh = 9km, Width = 9.1km Area = 9x 9.1 = 81.9 sq. kms. Area of the
map is 81.9 sq. kms.
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3.10. UTILITY OF TOPOGRAPHICAL MAPS:
Topographic maps, which are two-dimensional representations of
landforms and geographic features, are invaluable for landscape study
and often attractive works of art. What follows is a survey of some of the
major uses of these cartographic tools.
1. Route -planning
Study a topographic map from the U.S. Geological Survey or another
source to assist i n planning an itinerary to a wilderness region.
Backpackers and cross -country hikers especially need these maps to
route their travels along an efficient route (often with as little change in
elevation as possible), avoid obstacles (like landslides, deep canyons and
other generally rugged terrain), and locate water sources and potential
shelter.
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72 2. Safety & Survival
Choose a detailed -enough topographic map and keep it handy on treks to
ensure your personal safety. Sharing your route with friends and family,
not to mention other members of your own party, is made far easier with
the detailed geographic information coded in a topographic map. If you do
find yourself off-course, injured, beset by rough weather or otherwise
threatened, the map can help you find sp rings, high points (where cellular
phone and GPS reception might be stronger), nearby roads and buildings.
3. Professional and Scientific Uses
For planners, topographic maps can suggest potentially unstable
landscapes like landslide slopes, bottomlands or cut banks and eroding
shorelines that do not lend themselves easily to development. For botanists
and biologists, they can be overlain with other map layers, like
vegetation or soil zones, to predict species distribution. Developers might
scrutinize such depi ctions of terrain, in concert with other data, to identify
good spots for, say, wind -turbine placement. The applications are as
endless as geography's impacts on our lives.
3.11. SUMMARY:
After going through the unit we have come to know that the topographical
maps are sufficiently large scale maps prepared to show the micro details
of the ground. The variation in the relief, vegetation, land use, forms of
settlements, location of urban and market centre, drainage patterns,
transport network and communication lin es are some important
information given on the topographical map. These maps are usually
prepared and published by the official organization of national
government and cover the country in continuous series of maps at various
scale. Contour lines determine elevations of mountains and flat areas.
The closer together the lines are, the steeper the slope. Colours like
red, blue, brown and styles such as dotted, dashed, and curvy usually criss -
cross a topographic map. From the colour red on a toposheets we are able
o find out roads. The colour black indicates manmade or cultural features
while blue, brown, green show water - related features, contour lines and
elevation numbers, vegetation features respectively. White indicates any
landscape feature except for trees or water - including desert, grass,
sand, rocks, boulders, and so on. But remembering map colors is a fairly
trivial task.
Most topographic maps show more than just topography and are updated
periodically because changes occur in streets, roads, buildi ngs; other
infrastructure like power lines, wells as well as in boundaries and land-use
patterns.


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73 3.12. CHECK YOUR PROGRESS/ EXERCISE
1. True false
a. Closely spaced contours represent steep slopes while widely spaced
contours represent gentle slope.
b. The convex slope is fairly steep in the upper part and gentle in the
lower part.
c. A V-shaped valley occurs in lower course of a river.
d. A U-shaped valley is formed by strong lateral erosion of glaciers at
high altitudes.
e. On a map, a Spur is identified when the contours run very close to
one another, ultimately merging into one.
2. Fill in the blanks
a. The topographical maps represent the Earth’s features accurately and
to on a two surface.
b. Two contours of _ elevation usually do not
cross each other.
c. A hill with uniform slope and narrow top is represented by concentric
contours spaced almost at regular intervals.
d. The part of the U-shaped valley is shown by the innermost contour
line with a wide gap between its two sides
e. tints are colors used to indicate elevation, usually toget her with
contour lines.
3. Multiple choice question
a. The slopes can broadly be classified into
i. gentle, steep, concave, convex and irregular or undulating.
ii. big, small, concave, tall and irregular.
iii. sharp, pointed, gentle, steep, smooth and rough.
b. A gentle slope occur
i. when the degree or angle of slope of a feature is high and the
contours are closely spaced.
ii. a slope with a gentle gradient in the lower parts of a relief feature and
steep in its upper parts
iii. when the degree or angle of slope of a feature is very low.
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74 i. very widely -spaced contour lines on a map with the innermost
contour showing huge gap between its two sides.
ii. very closely -spaced contour lines on a map with the innermost
contour showing small gap between its two sides.
iii. very closely-spaced contour lines on a map with the outermost
contour showing small gap between its two sides.
d. In half-degree or half-inch map series
i. each of the degree sheet maps has been divided into 8 equal parts.
ii. each of the degree sheet maps has been divided into 4 equal parts.
iii. each of the degree sheet maps has been divided into 2 equal parts.
e. The contours representing a waterfall
i. merge into one another while crossing a river stream and the
rapids are shown by relatively distant contour lines on a map.
ii. the contours run very close to one another, ultimately merging into
one.
iii. the contour value increases with uniform intervals for all other contour
lines outward.
4. Answers the following Questions
1. Define of Topographical Map.
2. State the methods of showing relief and
landforms on Topographical Map.
3. What is Cross -section?
4. Discuss Topographical map index.
5. What are the various properties of contours
3.13. ANSWERS TO THE SELF LEARNING
QUESTIONS .
1.a. true
1.b. false, the convex slope is fairly gentle in the upper part and
steep in the lower part.
1.c. false, A V-shaped valley occurs in mountainous areas. 1.d.true
1.e. false, On a map, a cliff is identified when the contours run very close
to one another, ultimately merging into one.
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75 2.b. different
2.c. conical
2.d. lowermost
2.e. Hypsometric 3.a.i
3.b.iii.
3.c.ii.
3.d.ii.
3.e.i.
3.14. TECHNICAL WORDS:
 Contour lines: Contour lines connect a series of points of equal
elevation and are used to illustrate relief on a map. Numerous contour
lines that are close to one another indicate hilly or mountainous
terrain; when further apart they indicate a gentler slope; and when far
apart they indicate flat terrain.
 Projection: Geometricrepresentation of the curved surface of the
Earth on a flat sheet of paper.
 Relief : The physical configuration of the Earth’s surface , depicted on
a topographic map by contour lines and spot heights.
 Topography: Surface features both natural and man-made,
collectively depicted on topographic maps.
 Bearing: The horizontal angle at a given point, measured clockwise
from magnetic north or true north to a second point.
 Elevation: Vertical distance from a datum (usually mean sea level) to
a point or object on the Earth’s surface.
 Legend: A description, explanation table of symbols, or other
information, on a map or chart to provide a better u nderstanding and
interpretation of it.
 Magnetic north: Direction to which a compass needle points.
 Mean sea level: The average height of the surface of the sea for all
stages of tide, used as a reference surface from which elevations are
measured.
3.15. TASK
1. In a chart draw a complete conventional Signs and symbol sheet
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76
3.16. REFERENCES FOR FURTHER STUDY
❖ Gupta K. K and Tyagi V. C., 1992: Working with Maps, Survey of
India, DST, New Delhi.
❖ Singh R. L. and Singh R. P. B., 1999: Elements of Practical
Geography, Kalyani Publishers
❖ Sarkar A.K Practical Geography: A Systematic Approach, Oriental
Longman, Calcutta, 1997.
❖ Oxford dictionary

❖❖❖❖ 

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77 4
PREPARATION OF THEMATIC MAPS
After going through this chapter you will be able to understand the
following features:
Unit Structure
4.1 Objectives
4.2 Introduction
4.3 Subject discussion
4.4 Concept of Thematic Maps
4.5 Distinguishing characteristics of Thematic Maps
4.6 Variou s categories of Thematic Maps
4.7 Reading and interpretation of Thematic Maps
4.8 Utility of thematic maps of Thematic Maps
4.9 Techniques of representation of the theme of Thematic Maps
4.10 Interpretation and appreciation of Thematic Maps
4.11 Summary
4.12 Check your Progress/Exer cise
4.13 Answers to the self-learning questions
4.14 Technical words and their meaning
4.15 Task
4.16 References for further study
4.0. OBJECTIVES
By the end of this unit you will be able to:
 Understand the Concept of Thematic Maps
 Learn about Distinguishing characteristics of Thematic Maps
 Discuss Various categories of Thematic Maps
 EvaluateReading and interpretation of Thematic Maps
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78  Understand Techniques of representation of the theme of Thematic
Maps
 Learn Interpretation and appreciation of Them atic Maps
4.1. INTRODUCTION
In this unit we will study about the concept and the distinguishing
characteristics of Thematic Maps. There will be a discussion on the various
categories of Thematic Maps along with reading and interpretation of the
same. Utility of Thematic Maps as well as the techniques of representation
of the theme of Thematic Maps is very important. We will learn this in
this unit. Interpretation and appreciation of Thematic Maps will be
discussed in the latter part of this unit.
4.2. SUBJECT -DISCUSS ION
A map is a drawn or printed representation of the Earth. Visualization of
geographic and geo-referenced information is normally made through
maps. There are a huge variety of maps such as Political Maps, Physical
Maps, Contour Maps, Road Maps, Street M aps, Transit Maps, Thematic
Maps, Resource Maps and Inventory Maps. However maps can broadly be
classified into the following three main types:
1) General reference maps
2) Mobility maps
3) Thematic Maps
In this unit we are going to study Thematic Maps. A thematic map is a
map that emphasizes a particular theme or special topic such as the
average distribution of rainfall in an area whereas general reference maps
show natural features like rivers, cities, political subdivisions and
highways. These items are often present on a thematic map which is
simply used as reference points to enhance one’s understanding of the
map's theme and purpose.
Thematic maps show the distribution of a single attribute or the
relationship between several attributes. These maps can cover a variety
of characteristics from soil types to population density. Here the
cartographer bears the responsibility to make sure that the map shows the
correct distribution or the relationship between the various attributes.
Initially thematic maps were made with a small scale as the available data
was rather coarse, and importance was given to show the basic
distribution pattern than the map’s location for the data. However, with the
availability of better data thematic maps are made with a larger scale to
show more accurate spatial information at present. To make a good
thematic map a cartographer must be careful to portray the data on the
map when designing the same. This will in turn help one to use and
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79 marks and symbols that the cartographer uses to represent the data.
Moreover the sources of a thematic map's data are very important.
Cartographers must find accurate, recent and reliable sources of
information in a wide range of subjects v arying from environmental
features to demographic data to make the best possible maps. The designer
should also give an adequate locational base for the map.
4.3. CONCEPT OF THEMATIC MAPS
Thematic map is a map that emphasizes on a particular theme or a special
topic. Thematic map did not develop as a map type until the middle of 17th
century. Thematic maps are used to show soil types, vegetation, land use,
geology, etc. It also shows geographical concept like density and
distribution of population.
4.5 DISTINGUISHIN G CHARACTERISTICS OF THEMATIC
MAPS
Thematic map focuses on specific theme of subject area.
a. Sometimes the thematic map also emphasizes on spatial variation
of one or small number of geographic distribution.
b. Thematic maps are sometimes referred to as graphic essays.
4.6. VARIOUS CATEGORIES OF THEMATIC MAPS
There are many different types of thematic maps. Many types have been
designed for special purposes such as flow maps used in transportation
analysis. Thematic mapping is the process of shading a map according to a
given theme.
4.6.1.Common thematic map types include the following:
A. Choropleth maps
B. Dot density maps
C. Isopleth Map or Contour Maps
D. Proportional symbol maps
E. Colour patch
A. Choropleth maps
The term ‘Choropleth Map’ was introduced in 1938.The earliest known
Chorop leth map was created in 1826.Choropleth maps are most common
type of thematic map that usually portrays quantitative data as a colour
and can show density, percent, average value or quantity of an event
within a geographic area.Sequential colors on these maps represent
increasing or decreasing positive or negative data values. Generally, each
colour also represents a range of values.These maps represent a single
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80 ❖ Disadvantages of Choropleth Maps
Choropleth maps give a good visual impression of change over space but
there are certain disadvantages to using them:
 They give a false impression of abrupt change at the boundaries of
shaded units.
 Choropleth maps are often not suitable for showing to tal values.
Proportional symbols overlays (included on the choropleth map above)
are one solution to this problem.
 It can be difficult to distinguish between different shades.
 Variations within map units are hidden, and for this reason smaller
units are better than large ones.
B. Dot density maps
The Dot density maps show a symbol i.e. a dot for each individual or
group of individuals. These are used together with polygons and are useful
to show densities or values in a continuous way. These maps are
generally used to show multiple variables (e.g., through multiple colors,
dot sizes, symbols, etc.) but fails when many individuals or groups are
present. Dot density maps are only used when exact location is unknown.
❖ Demerits of Dot density maps
❖ The limitations of Dot density maps include the difficulty of
counting large numbers of dots in order to get a precise value and
the need to have a large amount of initial information before drawing
the map.
C. Isopleth Map
These maps are used for rendering differences in absolute or relative
values on a surface perceived as a continuum. Isopleth Maps use line
symbols to portray a continuous distribution such as temperature or
elevation. Isopleths are lines that connect points of equal numeric value.
One of the best-known types of Isopleth map is the contour map, which
shows elevation above sea level.
❖ The merits and demerits of Isopleth Maps are as follows:
• Merits
i. Isopleth are more scientific than other methods of showing
distribution and effectively show the distribution and variations.
ii. This is especially useful for climatic maps such as isobars,
isotherms, isohyets etc.and is known as the main tool for the
meteorologists.
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81 iii. It is very easy to determine the gradient (rate of change) with the
help of isopleth maps.
iv. When isopleth are wide apart, they show low gradient but when
they are closer together they show high gradient.
v. Isopleth lines are independent of political boundaries and best suited
to show the natural pattern of distribution of an element.
vi. Isopleth is the most suited method for showing elements having
transitional values, this is a reason that isopleth are invariably used
to show the distribution of temperature, pressure and other climatic
elements.
• Demerits
i. The drawing of isotherm often needs interpolation, which is a
difficult process.
ii. The method often suffers from lack of sufficient data.
D. Proportional symbol maps
Proportional symbol mapsareused for rendering absolute quantitative data.
These maps represent data associated with point locations such as cities.
The popul ations of different cities are frequently depicted on Proportional
symbol maps. Data is displayed on these maps with proportionally sized
symbols to show differences in occurrences. The symbols have different
sizes in proportion to some quantity that occur s at that point. Circles are
most often used with these maps but squares and other geometric shapes
are suitable as well.
E. Colour patch
Another type of thematic map is colour patch where colour is used for
identifying different groups. When these types of maps show urban or
rural settlements each of them is shown through different colours such as
if urban settlement is shown by red colour then rural is shown by yellow
colour.
4.7. READING AND INTERPRETATION OF THEMATIC
MAPS
To develop map reading abilities along with skills one should apply
certain basic principles to translate map symbols into landscape images. A
map reader must have ideas about the symbol as well as the landscape
present in real world. This is known as the perception of the symbols and
the real world. However when these two are revealed correctly the
understanding of the map will coincide exactly with the real world. How a
reader should interpret Thematic Maps have been discussed below.
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82 A Choroplethmap portrays quantitative data as a specific color and can
show density, percent, average value or quantity of an event within a
geographic area. There are several different types of color progressions
used by cartographers. Sequential colors on these maps represent
increasing or decreasing positive or negative data values. Usually, each
color represents a range of values. When there is a single -hue
progression fading from a dark shade of a specific color to a very light
shade of relatively the same hue the darkest hue represents the greatest
number in the data set while lightest shade represents the least number.
Dot density maps use dots to show the presence of a theme and display
a spatial pattern. The distribution of points on a map represents the
distribution of the given phenomenon in reality, and also shows the
change in the intensity or dispersion. Quantitative characteristics are
expressed using dots where each dot is attached by a particular value, for
example 1 dot = 100 people. For the distribution of dots, topographical
and cartogram approach es are used.
In an Isopleth map a line is drawn on a map through all points having the
same value of some measurable quantity. We visually interpret the
symbols to perceive areas of higher values and areas of lower values.
The information in the Isopleth maps can be interpreted through the
following ways:
a. Observe all points made from the base map.
b. Observe lines which pass in accordance to interval made, and these
lines direct the reader about the number of the same values from the
base map.
c. Observe the lowe st value and highest value and look on numbers
where lines pass according to the made interval.
d. Use color or shades if has been used to get more information.
The proportional symbol map is a widely -used form of thematic
mapping. In this technique, the cartographer selects a symbol and alters its
size based on the data values. The larger the symbol, the "more" of
something exists at a location. The symbols increase in size as the data
increase in value. In these maps the symbol sizes are directly proportiona l
to the data values. For example in a map of the 50 states there can be up
to 50 minutely different circle sizes, each one proportional to the number
it represents.
In colour maps cartographers utilize colour on a map to represent certain
features. Map co lors are always consistent on a single map as well as
across different types of maps by different cartographers or publishers.
Many colours used on maps have a relationship to the object or feature on
the ground. For example, blue is almost always the color chosen for fresh
water or ocean.
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83 4.8. UTILITY OF THEMATIC MAPS
Thematic maps serve the following three primary purposes:
a. They provide information about particular location.
b. They provide information about spatial pattern.
c. They can be used to compare patterns on 2 or 3 maps.
4.9. TECHNIQUES OF REPRESENTATION OF THE THEME
OF THEMATIC MAPS
I. Choropleth Map
Choropleth maps show statistical data. As the shades or pattern becomes
darker or denser the values increase. Choropleth maps provide an easy
way to visualize how a measurement varies across a geographical area.
❖ Usage of colors on Choropleth maps:
 Specific color progressions should be used to depict the data properly,
in a way that facilitates interpretation.
 Single -hue progressions fade from a dark shade of the chose n color to
a very light shade of relatively the same hue. Common method used to
show magnitude.
 Bi-polar progressions use two hues and are normally used to show a
change in data numbers from negative to positive.
 Blended hue progressions use related hues to blend together the two
end point hues. This type of color progression is typically used to
show elevation changes.
 Full spectral progression contains hues from blue through red. Usually
not recommended.
II. Isopleth Map or Contour Maps
Isopleth maps show a range of quantity. Isopleth maps usually have
ranges of similar values filled with similar colours or patterns showing
changes over space. Isopleth maps differ from Choropleth maps. In those
maps, the data is not grouped to define a region like a state or a country.
Isopleth are used to show climatic elements, temperature, pressure and
cloudiness. Care should be taken to show the index of concentration
before actually plotting them on the map while showing density of
population and distribution of crops etc. These maps are generated from
data that occur over geographical areas and values represent numerical
(quantitative) differences between features on an interval or ratio scale of
measurement.Isopleth maps also require a large amount of data for
accurate drawing.
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84 III. Dot Map
A Dot map is used as a distribution map or density map. Actually the
dot symbol shows the presence of a feature. These maps represent the
distribution of discrete phenomena with point symbols that each denotes
the same quantity.
❖ When constr ucting a dot map, two parameters must be considered:
a. the graphical size of each dot and
b. the value associated with each dot
❖ There are different types of dot maps.
a. One-to-one
In this type of dot map, each dot represents one single phenomenon since
the locati on of the dot corresponds to only on piece of data, care must be
taken to assure that the dot is represented in correct spatial location.
b. One-to-many
In this type of dot map, each dot on the map represents more than one
type of phenomenon being mapped.
IV. Proportional symbol Maps
The proportional technique uses symbols of different sizes to represent
data. For example: A square may be shown of each city to represent the
population of the respective cities in the map.
V. Colour patch
This map uses colour for ident ifying different groups, for example: The
map shows urban or rural settlements. Here urban are shown by purple
colour and rural are shown by yellow colour.
4.10. INTERPRETATION AND APPRECIATION OF
THEMATIC MAPS
As the name suggests, thematic maps are concerned with a particular
theme or topic of interest. While reference maps emphasize the location of
geographic features, thematic maps are more concerned with how things
are distributed across space. These maps are one of the most compelling
forms of information for several reasons. These are artistic and scientific.
These maps while preserving history clarify and reveal the invisible. We
also get information of the future. Regardless of the reason, these
maps capture the imagination of people around the world. One of the
strengths of thematic mapping is that it can make some abstract and
invisible concepts such as life expectancy around the world, per capita
gross domestic product (GDP) in Europe, or literacy rates across India
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85 4.11. SUMMARY:
After going through this unit of thematic maps we can conclude that these
maps are usually made with a single purpose in mind. Often, that
purpose has to do with revealing the spatial distribution of one or two
attribute data sets. We have also ex plored different types of thematic maps
and which type of map is conventionally used for different types of data
along with different goals. The discussed thematic maps include
choropleth, dot density, proportional symbol, isopleths and colour
patches. We have come to know that thematic maps are considered as
primary mechanism for summarizing and communicating the increased
volumes of geographically related information. In this unit we have learnt
about the most common thematic mapping techniques as well as their
interpretation.
4.12. CHECK YOUR PROGRESS/ EXERCISE
1. True false
a. A map is a drawn or printed representation of the globe.
b. Thematic maps are sometimes referred to as graphic essays.
c. Thematic mapping is the process of shading a map according to a
given time.
d. The term ‘Choropleth Map’ was introduced in 2017.
e. Isopleth Maps use line symbols to portray a continuous distribution
such as temperature or elevation.
2. Fill in the blanks
a. One of the best-known types of Isopleth map is the__ map, which
shows elevation above sea level.
b. Isopleth lines are independent of --------- boundaries and best suited to
show the natural pattern of distribution of an element.
c. The drawing of isotherm often needs -------------- which is a difficult
process.
d. ------------------ maps are used for rendering absolute quantitative data.
e. Sequential colours on--------------- maps represent increasing or
decreasing positive or negative data values.
3. Multiple choice question
a. The most common type of thematic map that usually portrays
quantitative data as a colour and can show density, percent, average
value or quantity of an event within a geographic area is known as
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86 i. Colour patch
ii. Choropleth map
iii. Dot density maps
b. The Dot density maps
I. use line symbols to portray a continuous distribution such as
temperature or elevation.
II. a dot is used together with polygons and is useful to show
densities or values in a continuous way.
III. circles are most often used but squares and other geometric shapes
are suitable as well.
IV. In an Isopleth map
i. a line is drawn on a map through all points having the same value
of some measurable quantity.
ii. quantitative data is portrayed as a specific colour and can show
density of population in a specific area.
iii. the symbol sizes are directly proportional to the data values.
V.In One-to-one dot maps
i. different coloured dots represent urban or rural settlements only.
ii. each dot on the map represents more than one type of phenomenon
being mapped.
iii. each dot represents one single phenomenon since the location of the
dot corresponds to only on piece of data.
VI.In Choropleth maps
i. bi-polar progressions use two hues and are normally used to show
a change in data numbers from negative to positive.
ii. use of each point symbols denotes the same quantity.
iii. isopleth is used to show elements having transitional values.
4. Answers the following Questions
1. What is a map?
2. What are the distinguishing characteristics of Thematic Maps?
3. State the disadvantages of Choropleth Maps.
4. Define Dot density maps and state its demerits of the same.
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87 6. How will you interpret Isopleth maps?
7. Define thematic maps. Elaborate your answer describing utility of
thematic maps.
8. What are the different techniques of representation of the theme of
Thematic Maps?
9. Write short notes on:
a. Choropleth maps
b. Dot density maps
c. Isople th Map or Contour Maps
d. Proportional symbol maps
e. Colour patch
4.13. ANSWERS TO THE SELF LEARNING
QUESTIONS
1.a. false, A map is a drawn or printed representation of the Earth.
1.b. true
1.c. false, Thematic mapping is the process of shading a map according
to a given theme.
1.d. false, The term ‘Choropleth Map’ was introduced in 1938
1.e. true
2.a. contour
2.b. political
2.c. interpolation
2.d. Proportional symbol
2.e. choropleth
3.a.ii
3.b.ii
3.c.i 3.d.iii
3.e.i

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88 4.14. TECHNICAL WORDS:
1. Maps : a diagrammatic representation of an area of land or sea
showing physical features, cities, roads, etc.
2. Cartographer : a person who draws or produces maps.
3. Reference map: It shows the location of the geographic areas for
which census data are tabulated and disseminated.
4. Mobility map : gives information on facilities and access in the city
centre for aged and disabled people.
5. Thematic Maps : A themat ic map is a map that emphasizes a
particular theme or special topic such as the average distribution of
rainfall in an area. They are different from general reference maps
because they do not just show natural features like rivers, cities,
political subdiv isions and highways.
6. Choropleth maps : a map which uses differences in shading,
colouring, or the placing of symbols within predefined areas to
indicate the average values of a particular quantity in those areas.
7. Dot density map : It is a map type that uses a dot symbol to show the
presence of a feature or phenomenon. Dot maps rely on a visual
scatter to show spatial pattern.
8. Isopleth : a line on a map connecting points at which a given variable
has a specified constant value.
4.15. TASK
1. In a chart show differen t techniques of representation of the theme
of Thematic Maps.
4.16 REFERENCES FOR FURTHER STUDY
• Gupta K. K and Tyagi V. C., 1992: Working with Maps, Survey of
India, DST, New Delhi.
• Singh R. L. and Singh R. P. B., 1999: Elements of Practical
Geography, K alyani Publishers
• Sarkar A.K Practical Geography: A Systematic Approach, Oriental
Longman, Calcutta, 1997.
• Oxford dictionary

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89 5
USE OF COMPUTERS IN
GEOGRAPHICAL DATA
REPRESENTATION
After going through this chapter you will be able to understand the
following features:
Unit Structure
5.1 Objectives
5.2 Introduction
5.3 Subject discussion
5.4 Constriction of Line and bar graph using MS - Excel
5.5 Constriction of the divided bar graph and pie charts using MS - Excel
5.6 Calculation of central tendency and standard deviation using SPSS
5.0. OBJECTIVES
By the end of this unit you will be able to:
 Understand Line and bar graphs,
 Discuss the Constriction of Line and bar graphs using MS - Excel
 Know the Constriction of the divided bar graph and pie charts using
MS- Excel
 Calculation of central tendency and standard deviation using SPSS
5.1. INTRODUCTION
In this unit we will study about Line and Bar graph which are
mathe matical representation of data. We will learn what are they used for
along with how to interpret the data presented in the same. Next we are
going to learn Importance and uses of Computer at first. After knowing
what a computer is we will learn about the B asic terms related to
computers. We will also learn MS Word and MS EXCEL. The Use of
Internet will be discussed in the latter part of this unit.
5.2. SUBJECT -DISCUSSION
Statistics is a special subject that usually deals with large numerical data
which can be represented graphically. In fact, the graphical representation
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90 is the representation of data by using graphical symbols such as lines, bars,
pie slices, dots etc. A graph does re present numerical data in the form of a
qualitative structure and provides important information. The most
astonishing part is that these graphs tell a story with visuals rather than
in words or numbers and thus help readers understand the substance of the
findings instead of the technical details behind each number. There are
innumerable graphing options to present data. In this unit we will learn
most popularly used ones such as line and Bar Graphs, Computer is the
wonderful and mastermind gift of the science to the humankind. The
term computer has been derived from the Latin term ‘computare’, which
means to calculate. Computer is an electronic device that is designed to
work with Information. It is a programmable machine and thus cannot do
anything withou t a Program. The two principal characteristics of a
computer are (a) it responds to a specific set of instructions in a well-
defined manner and (b) it can execute a prerecorded list of instructions i.e.
a program. It represents the decimal numbers through a string of binary
digits. The Word 'Computer' usually refers to the Center Processor Unit
plus Internal memory. The first mechanical computer designed by Charles
Babbage is known as Analytical Engine. It uses read -only memory in the
form of punch cards. Charles Babbage is called the "Grand Father" of the
computer.
We should remember one thing not to associate a personal computer with
the phrase computer. A personal computer or PC is a small and relatively
inexpensive computer. It is based on the microproce ssor technology and
designed for an individual use. Personal computers at home can be used
for a number of different applications including games, word processing,
accounting and other tasks. Besides PC there is Workstation which is a
powerful, single -user computer. Minicomputer is a multi -user computer
capable of supporting from 10 to hundreds of users simultaneously while
Mainframe is a powerful multi -user computer capable of supporting many
hundreds or thousands of users simultaneously. An extremely fast
computer that can perform hundreds of millions of instructions per
second is known as Supercomputer. Computers are used in many fields in
our daily life.
5.3. LINE AND BAR GRAPH.
5.3.1. A line graph is a graphical display of information that changes
continuously ove r time. It is a type of graph which displays information as
a series of data points called 'markers' connected by straight line segments.
A line graph has two axes. The x -axis of a line graph shows the
occurrences and the categories being compared over tim e and the y -axis
represents the scale, which is a set of numbers that represents the data and
is organized into equal intervals.
5.3.2. A bar graph is a pictorial presentation of statistical data and is
drawn using rectangular bars to show how large each value is. It is a
chart where bars are used to show comparisons between categories of
data. The bars are either horizontal or vertical. A bar graph has two axes
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91 “Average is an attempt to find one single figure to describe whole of
figures.”
- Clark other has numerical values that represent the values of the data. It does
not matter which axis is which, but it will determine what bar graph is
shown. If the descriptions are on the horizontal axis, the bars will be
oriented vertically, and if the values are along the horizontal axis, the
bars will be oriented horizontally.
Generally, the temperature and rainfall data of a particular station is
shown by combined line and Bar graph.
5.4. DIVIDED BAR & PIE CHART
DIVIDED BAR
In a Divided Bar Graph, a bar is divided into several segments t o represent
a set of quantities according to the different proportions of the total
amount. In divided bar charts, the columns are subdivided based on the
information being displayed. Divided bar charts are used to show the
frequency in several categories, like ordinary bar charts. It is a type of
compound bar chart. But unlike ordinary bar charts, each category is
subdivided.
PIE CHART
The “pie chart” is also known as a “circle chart”, dividing the circular
statistical graphic into sectors or sections to illustrate the numerical
problems. Each sector denotes a proportionate part of the whole. To find
out the composition of something, Pie -chart works the best at that time. In
most cases, pie charts replace other graphs like the bar graph, line
plots,histogr ams,etc.
Formula
The pie chart is an important type of data representation. It contains
different segments and sectors in which each segment and sector of a pie
chart forms a specific portion of the total(percentage). The sum of all the
data is equal to 36 0°.
5.5. MEASURES OF CENTRAL TENDENCY
In order to compare one set of data (1000 values) with another set of data
(1000 values) we require average or central number which represents the
entire data.

Average is normally value near to the middle value in the given data, so it
is also called as the Central value. Some values in the data are less than the
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92 e.g. Find out average of following numbers. 1, 2, 3, 4, 5
Let us add these numbers 1 + 2 + 3 + 4 + 5 = 15. Total number of
values = 5
1535Average
Average of the given numbers is 3.The average value, being central value
is also termed as Measures of Central Tendency. Different types of
measures of central tendency are
1) Mean
2) Median
3) Mode
5.6.1 MEASURES OF CENTRAL TENDENCY – MEAN
1) Mean - It is also termed as ‘average’ or arithmetic mean. It is obtained
by adding together all items and by dividing this total by the number of
items. xXn
Where X = Arithmetic average or mean
∑ X = Total of all values in the data.
n = Total number of values.
Find out mean of the following data 0, 10, 20 0 10 20 30X  21
1
1
2
11111 ( )
1
1 limMedian m cf
lover limit of the class
upper it of the class
f Frequency of the median class
m middle valuec Cumulative frequency of the preceding class  
   
    
   
 
     
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93 Total of all values in the data.
n = 3 Total number of values.
30103X
Xn  ( ) 10X Mean  
Ungrouped data
Mean - 1, 2, 4, 6, 8, 10, 10
∑ X = 1+ 2 + 4 + 6 + 8 +10 +10 = 41
n = 7 XXN
4175.85
The average value of the given data according to the Mean is 5.85
Grouped data - discrete - Mean -
Rainfall (in
cm) Regions
100 2
200 5
300 3

Rainfall (in
cm) X Regions f
fx
100 2 200
200 5 1000
300 3 900


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94 210010X
f
 210010210fXXfcms
 
The average amount of rainfall per region according to mean is 210 cms.
Grouped data - continuous - Mean -

Rainfall (in cm) X Regions f Mid point x
fx
0 - 100 4 50 200
100 - 200 10 150 1500
200 - 300 6 250 1500
∑ f = 20 ∑ fX = 3200
320020fX
f
 fXMean Xf
320020
160X
The average agricultural yield per region according to mean is 160
thousand tonnes.
Merits of Arithmetic Mean -
1) It is central value, it is the centre of gravity balancing values on
either side of it.
2) It is affected by the value of every item in the series.
3) It is easy to understand and calculate.
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95 5) It is useful for further statistical analysis.
Limitations of Arithmetic Mean -
1) Extreme values of the data affect Mean - e.g.
a) Average of 1, 2, 3 is 1 + 2 + 3 =6
6 ÷ 3 = 2
b) But average of 1, 2, 1002 is 1 + 2 + 1002 = 1005 ÷ 3 = 335 In the
second example the extreme value affects Mean.
2) It can not be calculated for incomplete data. i.e. all values are
required for calculation of mean.
5.6.2 MEASURES OF CENTRAL TENDENCY - MEDIAN
‘Median’ means middle value in a distribution (of data). Median splits the
observation into two parts. (lower & higher values) median is also termed
as a Positional average.
The term ‘Position’ means the place of value in a given data.
e.g.
Q.1 Find out median for the following data 1, 2, 4, 6, 8, 10, 10
Median -
1 12nMedianValue 
71
2
8
2
4thvalue

 2
4
6 ← Median
8
10
10

∴ The average value according to median is 6
Q.2 Find out median for the following data 3, 4, 2, 1, 5, 7
Let us rearrange numbers in proper order - 1, 2, 3, 4, 5, 7
As the number is even (six) the mid point will be between 3rd & 4th
value. Hence Median
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96 Grouped data - discrete Median -
Rainfall (in cms) - 100, 200, 300
Regions - 2, 5, 3
Rainfall (in cms) Regions f Cumulative frequency
less than
100 2 2
200 5 7
300 3 10
∑ f = 10

1 115.522th nMedian value   
As this number - (5.5th value) is more than 2 (cumulative frequency) but
less than 7, hence the median is located in the class whose cumulative
frequency is 7. the rainfall amount of this class is 200 cm.
∴The averag e amount of rainfall per region according to median is 200
cms.
Median -
Agricultural yield in
thousand tons Regions Cumulative frequency
less than
0 - 100 4 4
100 - 200 10 14
200 - 300 6 20
∑ f = 20

201022nm middle value    
∴ As number 10 is more than 4 but less than 14, median will be found
in the class 100 - 200 - (median class) ()21
111
11mcMedianf 
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97 4 10200 100100 (10 4)10
100100 (6)10
100 10(6)
100 60160m 



The average agricultural yield per region according to median is 160
thousand tonnes.
21
1
1
2
11111 ( )
1
1 limMedian m cf
lover limit of the class
upper it of the class
f Frequency of the median class
m middle valuec Cumulative frequency of the preceding class  
   
    
   
 
     
Merits of Median -
1) Extreme values do not affect the median.
2) It is useful for open and data as only the position and not the
values of items must be known.
3) It is easier to compute than the mean.
4) It can be used for qualitativ e data i.e. where ranks are given.
5) The value of median can be found out graphically.
Limitations of the median -
1) It is necessary to arrange data in proper order for calculation of
median.
2) As it is a positional average, its value is not determined by each and
every observation.
3) It is not much used for further statistical analysis.
4) The value of median is affected by sampling fluctuation than the
value of the arithmetic mean.
5. 6.3 MEASURES OF CENTRAL TENDENCY - MODE
The mode or the modal value is that value in a series of observations
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98 Mode - 1, 2, 4, 6, 8, 10, 10
Mode =1 - as 10 is the most common number in the given data.
The Mode, this word is derived from the French word ‘La Mode’ means
fashion. Where most of the people in the society use similar type of dress.
Mode is at the highest peak of the frequency curve.

Mode - Discrete series


← Maximum value - ∴ Modal class Mode =
20 cms.

The average amount of rainfall received by each region according to
mode is 200 cms.
Mode - Continuous Series



← Maximum value - Modal
class




Rainfall
(in cms) Regions
100 2
200 5
300 3
Agricultural production
in thousand tons Regions 0 - 100 4
100 - 200 10
200 - 300 6

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99 Mode
10
12 1
102
11 0 2
21( 1 1 )21 100, 10, 4, 61 200
10 4100 (200 100)2(10) 4 6
6100 (100)20 10
6100 (100)10
60010010
100 60160ff
fff
ff f     
 





The average amount of agricultural production per region according to
mode is 160 thousand tonnes.
The mode can also be obtained by using following formula based upon
the relationship between mean, median & mode.

Merits of mode -
1) It is easy to find mode in a given data.
2) It is not affected by the extreme values.
3) It can be used for the qualitative data.
e.g. Most preferred colour of dress by girls.

1) Alka - Pink
2) Swati - Blue
3) Narendra - Red
4) Sonali - Pink
5) Soni - Pink
6) Kshama - Red
From the data it is clear that 3 out of 6 girls prefer Pink and so mode is
pink colour. We can say that girls prefer pink dresses. Mode = 3 Median - 2 Mean
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100 4) The value of mode can also be obtained from frequency curve
(without doing calculation)
Limitations of Mode -
1) The value of mode cannot always be determined. - e.g. in the
bimodal (Two modes) or multimodal frequencies.
2) It is not multi used in further statistical analysis.
3) It does not include all items of the data.
4) It is not much used.
5.7 STANDARD DEVIATION
Standard deviation is the square root of the arithmetic average of the
squares of the deviations measured from the mean.
To find the S.D. the following steps are taken.
1) Find the deviations from the mean.
2) Square those deviations.
3) Find the mean of the sum of these deviations squared.
4) Find the square root of this mean.
Standard deviation -Grouped data - discrete.
Q. Find out S.D. for the following data.









Yield (in 000’ kg) (X) No. of regions (f) 40 10
45 15
50 25
55 30
60 28
65 13
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Geographical Data
Representation
101 7130130fxMeanf 







Ungrouped data - Standard deviation -
1, 2, 4, 6, 8, 10, 10

xMeann 4175.85 5.9XdXX


2tandS dard deviationn  
80.87
11.543.39 Yield
(X) Regions
(f) fx
40 10 400
45 15 675
50 25 1250
55 30 1650
60 28 1680
65 13 845
70 9 630
∑ f = 130 ∑ fx = 7130
X d d 2
1 - 4.9 24.0
2 - 3.9 15.2
4 - 1.9 3.6
6 0.1 0.01
8 2.1 4.4
10 4.1 16.8
10 4.1 16.8
∑ x = 41 ∑ d 2 = 80.8
munotes.in

Page 102

Tools and Techniques in
Geography for Spatial
Analysis -I
102 ∴Standard deviation of the given data is 3.39. Standard deviation - ungrouped data. Find out S.D. for the following data.
Height (in inches) 60, 60, 61, 62, 63, 63,63, 64, 64, 70
Height (in
X Deviations from
mean (63°)
d
d 2 xMeann
60 - 3 9


630
10
63()XX

 60 - 3 9
61 - 2 4
62 - 1 1
63 0 0
63 0 0
63 0 0
64 +1 1
64 +1 1
70 +7 49
∑ x = 630 ∑ d 2 = 74
2tandS dard deviation orn     
74107.42.72


∴ Deviation in height according to Standard deviation is 2.72 ′ .
Group data -
Standard deviation - Continuous series.
Find out S.D. for the following data.
Rainfall (in
cm) Regions
0 - 100 2
100 - 200 5
200 - 300 4
300 - 400 2
munotes.in

Page 103

Use of Computers In
Geographical Data
Representation
103 (in cm) Mid point X
f
fx fxMeanf
2550
13
196.15()dX X

 0 - 100 50 2 100
100 - 200 150 5 750
200 - 300 250 4 1000
300 - 400 350 2 700
∑ f = 13 2550

Rainfall (in cm) Mid point
X
f Deviation
from
mean
196.15
(d)
fd
fd 2
0 - 100 50 2 - 146.15 292.3 42719.6
100 - 200 150 5 - 46.15 230.75 10649.1
200 - 300 250 4 53.85 215.4 11599.3
300 - 400 350 2 153.85 307.7 47339.6
∑ f = 13 ∑ fd = 1046.2 ∑ fd 2 = 112307.6
2fdf
112307.613
8639
92.95cms


∴ Rainfall variability according to S.D. is 92.95 cms.





munotes.in

Page 104

Tools and Techniques in
Geography for Spatial
Analysis -I
104 Standard Deviation
Mean
2100
10210FXF
xDXX




Rainfall
(in cm) X Regions

f Deviation from
mean =210
d
fd
fd 2
100 2 - 110 - 220 24,200
200 5 - 10 - 50 500
300 3 90 270 24,300
∑ f = 10 ∑ fd 2 = 49, 000
2..fdSDf 49000104900

S.D. 70 cms. Of rainfall
Variation in the amount of rainfall according to standard deviation is 70
cms.
Standard deviation -






Rainfall
(in cm) X Regions

f

fx
100 2 200
200 5 1000
300 3 900
∑ f = 10 ∑ fx = 2100
Agricultural
Production in
thousand tonnes Mid point X Regions f
fx
0 - 100 50 4 200
100 - 200 150 10 1500
200 - 300 250 6 1500
∑ f = 20 ∑ fx = 3200 munotes.in

Page 105

Use of Computers In
Geographical Data
Representation
105 320016020fxMeanf   160 . ( )X thousand tons d X X  






2tanfdS drad Deviationf  
98,00020490070


The variation in the agricultural production among diff regions
according to standard deviation is 70 thousand tons.
Merits of S.D.
1) It is the best method of deviation.
2) It is based on every item of the distribution.
3) It is used in further statistical analysis.
Limitations of S.D.
1) It is difficult & time consuming to calculate than other methods.
2) It gives more weight to extreme items & less to those which are near
the mean.

❖❖❖❖ Agricultural
Production
in thousand
tons Mid
point
X Regions
f Deviation
from
mean
160 d
fd
fd 2
0 - 100 50 4 - 110 440 48,400
100 - 200 150 10 - 10 100 1000
200 - 300 250 6 90 540 48600
∑ f = 20 ∑ fd 2 = 98, 000
munotes.in