map reading unit 1.pdf

1.1 Map Concepts and Definition
• A map is a simple scaled down representation of part or the
whole surface of the earth.
• Maps are two-dimensional models (abstractions) of the surface
of the earth.
• They portray the distribution of features, characters or
phenomena.
• A model is defined as an idealized representation of the real
world built in order to demonstrate certain of its properties.

Cont’d
• According to the International Cartographic Association,
a map is
 a representation, normally to scale and on a flat medium, of
a selection of material or abstract features on, or in relation
to, the surface of the Earth.
• The term ‘map’ is often used in mathematics to convey
the notion of transferring information from one form to
another, just as cartographers transfer information from
the surface of the Earth to a sheet of paper.

Cont’d
• Production of a map requires
 selection of the few features in the real world to include,
 classification of selected features into groups (i.e., roads, houses,
railways),
 Simplification of jagged lines like river meandering,
 exaggeration of features to be included that are to small to show
at the scale of the map and
 symbolization to represent the different classes of features
chosen.
• Maps provide useful ways of displaying information in a
meaningful way.

1.2 Classification of Map
• There are many types of maps. Most of these maps are
grouped into two major types of:-
A.Topographic map:
 These maps are a reference tool, showing the outlines of
selected natural and man-made features of the Earth, often acts
as a frame for other information.
 ‘Topography’ refers to the shape of the surface, represented by
contours and/or shading, but topographic maps also show
roads and other prominent features.

A. Topographic Maps
• The word topography is derived from the Greek word topos, which
means place.
• Topography is a term used to describe all physical features of a given
area. Topographic maps are small-scale drawings of a part of the
earth’s surface. These maps show:-
(a) Location
• The geographic location in a map may be shown by using:-
(i).Compass bearing. (ii) Grid reference.

Cont’d
(iii) Latitude and longitude. (iv) Political and administrative boundaries.
(v) Use of place names.
(b) Landscape
 Some of the landscape features shown on a topographic map are
mountains, hills, plateaus, plains, lakes, rivers, seas, oceans and
shape of coast lines.
(c) Cultural features
Some of the cultural features or artificial features are roads, railways,
cities, towns, dams and other structures built by man.

B. Thematic or Distributional
Maps
• The statistical or distribution maps are the type of maps which have
been made with the help of exact statistics.
• These maps show such things as distribution of rainfall, temperature,
pressure, vegetation, crops, minerals and many other things.
• The commonly used Statistical or Distribution maps are the Atlas
maps.
 Atlas Maps are (a) maps drawn on small scales.
(b) They show whole countries, continents or even
the world on a single sheet of paper or page.

Cont’d
(c) They show generalized information. They do not include or show a
great amount of detail as shown in topographic maps.
(d) Atlas maps my be drawn on one map and include and show the
distribution of many things such as crops, minerals, roads, railways,
towns, relief, vegetation and many others. Such details may be shown
by the use of colors, signs and symbols.
(e) Atlas maps are simple, easy to read and interpret. They are easy to
draw or to reproduce.

Uses of topographic maps
I. Topographic maps are useful for describing features of the earth’s
surface.
II. People use maps t reach their direction. That is the direction where
to go and how far to go.
III. Builders use maps to plan the best use of land.
IV. Road builders use maps to design new roads.
V. Farmers use maps to plan the best use of their farmlands.

Uses of the Thematic or
distribution maps.
I. Physical maps show the arrangement or the distribution of
mountains, hills, uplands, lowlands, rivers and so on.
II. Political maps show areas with their political and administrative
boundaries.
III. Climatic maps show the distribution of temperatures, rainfall,
pressure, winds, climatic regions, etc.
IV. Historical empires and historical sites, for example. Olduvai Gorge.
V. Economic maps show the distribution of chief crops, animals,
industries, roads, mines, etc.

1.3 Uses of Maps
Nowadays maps have several uses. The following are basic ones.
 To locate: A map shows the exact site of place as well as the situation. As the
geographical mobility of people increase, the use of maps for vocational purpose also
increases.
 To measure distance: With the help of a map distance between place could be
measured.
 To calculate area: The size of a certain place or land or a country can be calculated
from maps.
 To identify direction: we can read the direction of objects placed from one another on
maps.
 To discover relationship between different phenomena by analyzing map information.

2. Map Scale
2.1 Concepts and Definition of Scale
• A scale is the relationship or ratio between the distance on map and
the true distance on the earth’s surface.’
𝑆𝑐𝑎𝑙𝑒 = 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑜𝑛 𝑡ℎ𝑒 𝑚𝑎𝑝
𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑜𝑛 𝑡ℎ𝑒 𝑒𝑎𝑟𝑡ℎ 𝑠𝑢𝑟𝑓𝑎𝑐𝑒
The uses of scale:
 Helps map interpreter to calculate distance, area and computation of
other facts.
 Helps contractors, engineers to design appropriate plans for bridges,
railway lines etc.

Cont’d
 Helps economists and geographers in establishing the projects.
 Helps map maker to represent a part of the earth’s surface on a small piece of
paper.
 Helps map makers t draw maps.
2.2 Methods of Scale
Representations
 There are three types of scales:-
1. Statement scale.
2. Representative fraction scale.
3. Linear Scale.

1. Statement of scale
• This is the way of expressing the scale by using words. Example:
1:500,000 or 1cm to 5km.
• This means that one centimeter on the map represent five kilometers
on the actual ground.
NOTE: Statement scale is written in cm to km.
2. Representative Fraction
 This is the way of expressing the scale by using ratio and fraction.
 The R.F scale is written in the form of centimeters.

Cont’d
• A representative fraction or R.F. in short is a means of expressing the
relative size o f a map or drawing in terms of a fraction.
• R.F. scale is frequently expresses as a fraction with the numerator as
one.
• The ratio means that-One unit on the map represents a given
number of units on the ground.
• One centimeter equals to one kilometer. This scale means that 1 cm
on the map represents 100,000 cm on the ground.

Cont’d
e.g. 1:500,000 write into the R.F scale
 As a ratio = 1:500,000
 As a Fraction = 1/500,000
3. Linear Scale
• Linear scale is the way of expressing the scale by using line divided
into sections and each section represent one centimeters on the
map, or linear scale is the way of expressing scale by using line.

Cont’d
• Linear scale is a way of depicting the scale using line divided into
sections and each section represent one centimeter on the map.
• Linear scale has two parts, namely;
1) Primary division
 This is important part of linear scale which is located at the right
hand side of the graph and its shown by kilometers or miles.
 Example, Construct the linear scale by using the scale of 1:600,000

Cont’d
Solution
 Linear is a way of expressing the scale by using
line that divided into sections and each section
represent one centimeter on the map.
 to change 1:600,000 into kilometers
100,000 = 1km
600,000 = ?
= 600,000 𝑥 1𝑘𝑚
100,000𝑐𝑚
= 6km
= 1cm to 6km

Cont’d
• LINEAR SCALE DIAGRAM
• Where by
– M-meters
– Km =kilometers
2. SECONDARY SIVISION
This is also an important part of the linear scale which is found at left
hand side of the graph and is shown by using centimeter or meter.

2.3 Construction of Linear
Scale
• Graphical scale is essential for representation of map while reduction or
enlargement of map has been done.
• Graphical scale is also called as linear scale as it is represented by a line.
• This line can be divided into certain parts to show ground units.
• Each part of the line is representing length between two points on the map
and unit shows ground distance between those points.
• These parts of line are called Primary divisions.
• Graphical scale always shows ground unit only.

• Graphical scale has reference of verbal scale in any system.
• You can represent the graphical scale in any of the below mentioned
formats.

Rules to construct Graphical Scale:
1. To draw a graphical scale you must need a verbal scale. If you have RF
then first convert this into VS. and then proceed further.
2. In metric system the length of graphical scale is about 8 cm to 12 cm. And
in British system it is 4 inches to 8 inches.
3. First we have to do primary divisions according to scale.
4. 0 zero should be written on second place because at left side we have to
show secondary units.
5. Always write ground distance on line to represent the ground length
according to scale.

Example: Construct a simple graphical scale for following verbal scale.
1 cm = 10 km
• If the length of graphical scale is 10 cm then,
10 cm = 10 * 10 km
• 10 cm = 100 km (10 cm of graphical scale will represents 100 km on the
ground
• Now next step, if we divide the line of 10 cm in 5 equal parts, each part will
be of 2 cm and represents 20 km on the ground.
10 / 5 cm = 100 / 5 km
2 cm = 20 km

 Draw a line with the length of 10cm. Divide this line into 5 equal parts of 2
cm each.
 Each part of 2 cm will represent 20 km on the ground.
 Start 0 zero from second place and write ground unit (km) in front of it.
 At the last 80 km number will be there. These are primary divisions.
 At the left side Secondary divisions will be there, which are represented in
meters here.
 10 km = 1cm, therefore at the secondary division 1cm and 2cm number
will be there.
20 10 0 20 40 60 80km
Primary Division
Secondary
Division

2.4 Types of Scale
• Basically map makers use the following two types of scale. Namely
- Linear scale
- Areal scale
 Linear Scale: is a kind of scale, which gives us the proportional relationship
between lines or distance on maps and lines or distance on the ground.
Linear scale = distance on the maps/distance on the grounds.
Example 1cm to 1km.
 Areal scale: on the other hand refers to the proportional relationship
between areas on the map and actual area on the ground. Example 1𝑐𝑚2
to 4𝑐𝑚2.

 Areal scale is the square of linear scale. For example, if a map has a
linear scale of 1 cm to 6 km, then the areal scale of the map is
(1𝑐𝑚2
, 6𝑘𝑚2
), which means 1𝑐𝑚2
𝑡𝑜 36𝑘𝑚2
.
 Areal Scale = (𝑙𝑖𝑛𝑒𝑎𝑟 𝑠𝑐𝑎𝑙𝑒)2 =
(𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑜𝑛 𝑡ℎ𝑒 𝑚𝑎𝑝)
(𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑜𝑛 𝑡ℎ𝑒 𝑔𝑟𝑜𝑢𝑛𝑑)
2

2.5. Method of Enlargement and
Reduction of maps
• Enlargement: We enlarge a map when we need to show more details
(features) about the area it shows. Often, enlarged maps are
produced in order to support detailed study of the area that the map
presents.
• We enlarge a map by enlarging its scale. The size of the paper on
which the new map is printed increases in proportion to the new
scale. Example: city maps are often enlarged maps.
• An enlarged map would be quite helpful for demonstrating the
required area for a class room

Reduction: We reduce maps when we need to be selective and to generalize
the information that the map presents.
When the scale of the map decreases, the size of the map also decreases
accordingly. When you enlarge or reduce a map, consider these principles: if
a map is to be enlarged x times, the new map will be x times the scale of the
old map. If you reduce a map by 1/x, the scale of the new map will be 1/x
times the scale of the old map.
Example 1
If we enlarge a map with a scale 1:200,000 two times, what will be the scale
of the new map?
Solution:
Previous scale = 1: 200,000 or 1/200,000

The scale of the new map = 1/200,000 × 2 = 1/100,000 or 1:100,000
The scale of the new map (1:100, 000) is two times larger than the scale of
the old map, (1: 200,000)
Example 2
If we reduce a map with a scale 1:50,000 by half, what will be the scale of
the new map?
Solution:
Previous scale = 1:50,000
The scale of the new map = 1/50,000 × 1/2 = 1/100,000 or 1:100,000
The scale of the new map (1:100,000) is half of the scale of the old map
(1:50,000).

The amount of increase or reduction of scale can be obtained by applying
the following formulae:
1 Amount of enlargement = The denominator of the small scale
The denominator of the large scale
Example 3
A map at 1: 200,000 is to be enlarged to a map at 1:100,000. By how
many times is the scale increased?
Amount of increase = 200,000/100,000 = 2 times
2 The amount of reduction = Denominator of large scale
Denominator of small scale

Example 4
A map with a scale of 1: 50,000 is reduced to 1:1000,000. How many
times is the scale reduced?
Amount of reduction = 50,000/100,000 = 1/2 times

3. Graphic Representation and
Interpretation of Geographic Data
3.1 Marginal and Boarder Information
 Marginal information of maps is explanatory notes, diagrams and scales
shown on the margins of topographic maps.
 As a matter of fact, every modern map has it own marginal information
useful to map users.
 The following are selectively the most vital information that appear on the
margins of topographic maps:

a) Sheet name or title of the map: is printed at the top.
b) Sheet number and series:
c) Scale of the map:
d) Key to conventional signs and symbols:
e) Publisher and copy write owner:
f) Boundary diagram:
g) North arrow: Most modern maps are printed with north at the top.
h) Nationality: The name of the country together with R.F is printed to the
margin of each topographic sheet.
i) Type of projection used: Ethiopian topographic maps are made on the
Mercator projection.
j) Unit of measurement:

3.2 Determining Scale.
Distance and Area From Map
3.2.1 Measurements of distance on maps.
• All distances obtained through measurements on maps and the use of the
scale only are called Map Distances (MD) which are expressed in cm.
• Map distances don’t consider the ups and downs of the land surface.
• On the other extreme, distances obtained through measurements on maps
using the scale and some calculations, which take into consideration the
ups and downs, are called the Actual of Field Distance (FD).It is expressed
in km. or meter.

 MD = aerial or straight distance
 FD = irregular ground distance considering the ups and downs of the
earth’s surface.
1. Distance along a straight line
• A straight line distance is the one measured simply along a straight line
without considering the real earth‟s features. It is called air distance or
crow flies (bird eye view).
• In other words, it is a type of distance that refers to the measurement of
map distance between two points that is obtained directly by using ruler
and the scale of the map.
E.g. Find the map distance of the following map.

Scale: RF. 1:50,000
Procedures:
1. Measure the distance between the two points (A&B) using a ruler (let
it be 5cm.)
2. Determine the map distance using scale that must be expressed in
km. or meter. Use the following mathematical formula.
A
B

MD =
𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑜𝑛 𝑡ℎ𝑒 𝑚𝑎𝑝 𝑥 𝑆𝑐𝑎𝑙𝑒
100,000
MD = 5cm x 50000/100000 = 2.5km.
2. Distance along curved line.
• Distances along curved line are also called Bending line distance.
• Distance along roads, railways, rivers and coastal lines can be measured
using the principle of bending line distance.
• To find the distance on the map in the case of bending line distance in
addition to the ruler we need to use threads, string the edge of a plain
sheet of paper or a pair of divider.

E.g. find the distance between point A and point B along the road.
Scale RF. 1:40000
Procedure:
1. Divide the curved line (A to B) by light pencil marks into nearly straight
portions or sections.
2. Carefully measure each of these straight sections, or transfer the section
directly to the edge of a piece of paper or thread.
A
B

3. Using a ruler directly find the total distance between the points of the
dividers or thread (let it be 10cm.)
4. Determine the map distance between A and B using the formula how to
find the map distance.
MD =
10𝑐𝑚∗40,000
100,000
= 4km
3. Field Distance
 Field distance, which is also called Actual distance on the ground, takes
actual earth’s condition i.e. the ups and downs into consideration.
 To find the FD we must follow the following steps.
1. Obtain map distance between the two points with the help of
measurement, scale and some calculation.

2. Obtain altitude difference between the two points. Note that, both MD
and AD should be in the same unit of measurement.
3. Apply the Pythagoras theorem ( 𝐶2
= 𝑎2
+ 𝑏2
) as 𝐹𝐷2
= 𝐴𝐷2
+ 𝑀𝐷2
Find the Field Distance between point A and B along the road shown
on the map.
 Find Map Distance (MD) measure the distance from point A to B by
drawing straight line (let it be 6.5 cm.) 6.5 x 50000/100000 = 3.25 km.
 Find Altitude Difference (AD) by using the altitude expressed by contour

lines of each point ( 2900m-2400m = 500m/100 = 0.4km.).
 𝐹𝐷2
= 𝐴𝐷2
+ 𝑀𝐷2
= 𝐹𝐷2
= 3.25 𝑘𝑚2
+ 0.4 𝑘𝑚2
FD = (3.25 𝑘𝑚2) + (0.4 𝑘𝑚2)
FD = 10.5625 𝑘𝑚2 + 0.16 𝑘𝑚2
FD = 10.7225 𝑘𝑚2
FD = 3.2745 KM
FD
AD = 0.4km
MD = 3.25km

3.2.2. Measurement of Area
on the Map
• The area of something such as a piece of land total extent is measured in
square or rectangle or triangle in mile or km. or in inch or meter.
• In map exercise, it may be possible to measure or calculate two types of
areas : Regular and irregular shapes.
A. Regular Area
o Are those which have defined shapes whose area can be measure d or
calculated using the plane geometry or mathematical formulas.
o These include:

 Square = 𝑠2
 Rectangle = Lx W
 Triangle = B x H /2 or ½ x b x h
 Circle = 𝜋𝑟2
 Sphere = 4𝜋𝑟2
Example: find the area of a farm whose base is 5cm and height is 4cm on a
map scale with a scale of 1:100,000.
Actual base = 5𝑐𝑚 𝑥 100,000
100,000
= 5km
Actual height = 4𝑐𝑚 𝑥 100,000
100,000
= 4km
1:100,000 Area of farm =5km x 4km = 20𝑘𝑚2
4cm
5cm

map reading unit 1.pdf

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map reading unit 1.pdf