Maps are generally drawn accurately so that there is a definite proportion between features on the ground and those on a map. The scale of a map is the ratio which the distance between any two points on a map bears to the actual distance between the corresponding points on the ground. Thus, if the scale of a map is 1 cm to 1 km, it means that a distance of 1 cm on the map indicates 1 km on the ground. Thus, if distance between two villages on that map is 6.2 cm, it means that the actual distance on the ground will be 6.2 km.
The scale of a map may be indicated in three different ways:
(i) as a statement, e.g., one cm to 1 km, or 5 cm to 1 km, etc.
(ii) as a fraction called Representative Fraction (R.F.).
e.g. 1/100,000 or 1:100,000; or 1: 50,000, etc. The numerator of the fraction is always one. Any unit of length can be used with the R.F. If a map has R.F. of 1:50,000, it means 1 cm: 50,000 cm or 1 in. = 50,000 in. The Representative Fraction = Distance on the map/ Distance on the ground
(iii) as a linear scale. The linear scale is a line of convenient length marked at the bottom of a map and graduated in distances on the ground. The line is divided and subdivided into units to enable precise measurement. The distance between two points on a map can be measured by a pair of dividers and the dividers can be placed on the linear scale and actual distance may be obtained in the units marked on the linear scale.
Maps are classified into large scale maps and small scale maps. Large scale maps like topographic maps on a scale of 1:50,000 show a great deal of information about a small area. Small scale maps show a large area on a small size map. An atlas map is a small scale map. The scale may be 1:10,000,000. Small-scale maps do not show many details. A map with R.F. of 1:20,000 is a large-scale map compared to a map with R.F. of 1:50,000.
Sketch maps are not drawn to scale. They indicate relative positions only and not actual distances or directions. A plan refers to a building or a room. It indicates the site of a school or classrooms etc. Plans are drawn to scale to show accurately location of doors, windows, etc.
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