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Get the answer of: Why a scale is must in a map?
Drawing actual shape of Earth on paper is known as map. It is always smaller than the actual size of Earth or a part of it. In other words original distances are represented on maps according to a fixed ratio. The ratio of distance shown on the map and the actual distance on earth is known as scale. e.g. on an map if distance between two points is 1 cm and distance between those two places on earth is 5 kms, then the scale of map will be 1 cm equal to 5 kms.
We can easily understand the scale of map through air travel or observation. The view, we get while sitting in a plane, flying thousands feet high from surface, is a form of map.
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Representation of Scales:
Basically scales of maps are represented in three ways:
1. Statement of Scale
2. Representative Fraction (R.F.)
3. Linear Scale.
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1. Statement of Scale:
In this method a statement is given about the scale of the map e.g. 1 inch shows 2 miles. This statement can make even a lay man understand that an inch of distance on map is showing 2 miles of actual distance on Earth. This form of expressing scale is perhaps the simplest form but various units of showing distance are used world over.
Therefore, any statement may not have any meaning for those people who do not use the unit of distance as shown in a statement. Secondly the importance of statement vanishes if we enlarge or reduce a map because change in scale gives birth to various problems in measurement of distances.
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2. Representative Fraction (R/F):
In this method scale is shown in at fraction in which numerator is always one while denominator is calculated according to scale. The distance on map is shown in a particular ratio to the actual distance on Earth. The distance on map is one unit (Numerator) while actual distance is denominator units. e.g. If R.F. is shown as 1/1,00,000 Then it means that 1 cm on map shows 1,00,000 cms on Earth or 1 inch on map shows 1,00,000 inches on Earth on the actual distance. Similarly, R.F. may be applied on any unit of distance.
The greatest benefit of this method of showing scale is that an observer of map can use any unit of distance of his choice while studying it. That is why R.F. method is also known as Numerical Fraction Method and even International Method.
For various maps prepared in India R.F. method of showing scale was deemed particularly beneficial in 1957 when India adopted to metric system of measurement. Prior to 1957 the distance shown in Indian maps was in inches, feets, yards furlong & miles. R.F. method made it possible to study that system in metric form.
Despite various positive characteristics of R.F. method of showing scale, biggest weakness is that it is quite difficult for layman to understand it. Secondly, reduction and enlargement of map brings in various other problems of measuring distances.
3. Linear Scale:
A straight line measuring about 15 cm or 6 inches, divided in various parts shows the scale in linear method. It is quite easy to show distances on scale representing actual distances. The sub part of linear scale at the left is further divided into sub parts which show smaller units of distance more accurately. This method excludes the drawbacks of previous two methods. With the help of this method the scale remains accurate whether we increase or decrease the size of map. But this requires more time and better technique.
Use of Scale in Maps:
Each map is incomplete without scale. To represent the relief on map accurately it is necessary that the distances between different places on Earth should be shown after reducing according to a fixed ratio. With the help of these shapes, sizes, distances, and directions of various places shown on map, look according to the real situation. This is possible only with a scale. Map drawn without scale would be a picture or sketch.