Introduction to Map Reading

Geography is the study of the inter-relationship of man and his physical environment. For such a study the map is useful tool, as it provides a survey of the distribution of the various geographical features over a large area. For example, the topographical map furnishes the student with detailed information of both the physical and cultural environment. Thus the student who knows hoe to interpret a map will be able to grasp the complex ideas of relationships derived from the different items depicted on the map.
Inasmuch as maps are source of information, they are also a means of presenting geographical data, and a supporting evidence in geographical writing.
To ensure that the student is able to make use a maps in both aspects, we will first introduce the fundamental concepts of map-work, particularly those of topographical maps.

SCALE
Scale implies a ratio. When we speak of the scale of a map, we are, in fact,speaking of the proportion which a length of the maps bears to the actual distance on the ground. For example, when we say that the scale of a map is one inch to a mile, we mean that the distance of one inch on the map is equal to one mile in actual distance on the ground Scales allows us to calculate distance between place depicted on maps.
A scale representing a shorter distance on the ground is said to be "larger" then one representing a longer distance.
A scale may be expressed in one of the following ways:
(i) In the form of a statement- " 1 inch to a 1 mile ".
(ii) By means of a linear or line scale
(iii) As a Representative Fraction (R.F)-- 1: 63,360 or 1/36,360. The numerator 1 indicates the measurement on the map while the denominator, 63,360, indicates the actual distance on the ground. Notice that the numerator is always a unity, 1, and no units of measurement are denoted. Representative Fractions can easily be converted into line scales and vice versa.

Example: 1
Find the Representative Fraction, if the scale given is 1 inch = 2 miles.
1 inch on the maps represents 2 miles on the ground.
* 1 inch on the map represents (2 x 1,760) yards or 3,520 yards on the ground.
To chage 3,520 yard into inches: 3,520 x 3 x 12 = 126,720 inches.

Example: 2
The Representative Fraction of the maps is 1:100,000.
What is the statement of scale in centimetres and and kilometres?
1 Centimetres on the map represents 100,000 centimetres on the ground.
Since 100 centimetres = 1 metre and
1,000 metres = 1 kilometre
* 1 centimetre of the maps reresents
100,000/(100x1,000) or1 kilometre.
*The scale is 1 centimetre to 1 kilometre.