GIS: TYPES OF MAP SCALES

MAPS AND MAP SCALES

Map Scale

The size of earth is too big to be represented as it is on a map. It is the relationship between distance on map and distance on ground that tells what distance on map corresponds to what distance on ground.

Representation of scale

 There are three ways in which a scale can be depicted on a map:

Expressed in words such as ‘2 centimeters to the kilometer’ which means two centimeters on the map represents one kilometer on the ground. Though it is the simplest way of expressing a scale but it has the following drawbacks associated with it:

1. Statement

-The fractional distances involve mathematical calculations

-Different countries have different units of length, expressing a statement scale on a map may not be understood by the foreigners.

2. Representative fraction

It is expressed in fraction. If the scale is 1:50000, it means that 1 unit of measurement on map represents 50,000 units on ground. It is also known as numerical scale.

The distance on map and the distance on the ground must be in the same units of length.

The advantage of this scale is that- it can be read into different units of length. For example the map with a scale 1:50,000 would mean that a distance of 1 cm on ground represents 50,000 cm on the ground or it can also be said that a distance of 1 feet on ground represents 50,000 feet on ground.

3. Graphic:

The scale is shown in form of a strip, where the strip is divided into a number of equal parts and is marked to show what these divisions represent on actual ground. It is also known as plain scale or linear scale.

For example, the scale represents that 1 division of a strip on map represents 10 km on ground.

The advantage of a graphic scale is that it is reduced or enlarged in the same proportion in which the map is reduced or enlarged.

Copyright IIT Delhi

 

 

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