Graphical scale

Geography glossary

Also called: Bar scale, Linear scale · Topic: Maps and Map Scale · NCERT: Class 11, Ch 2 "Map Scale"

Meaning

A graphical scale, or bar scale, is a straight line drawn on a map and marked with ground distances. The bar is cut into primary parts (main units, such as kilometres). The left-hand part is cut into smaller secondary parts (such as 100 m). Its special strength is that it stays correct when the map is enlarged or reduced. This is because the bar grows or shrinks along with the map. Its weakness is that it can only be read in its own units.

Example

For a 1:50,000 Survey of India toposheet, take a line of 15 cm, which equals 7.5 km. Round it off to 10 cm = 5 km. Divide it into 5 primary parts of 1 km each, and split the left part into 100 m units.

Don't confuse with

  • Statement of scale: written in words, such as "1 cm represents 10 km". It becomes wrong if the map is photocopied larger or smaller.
  • Representative fraction (RF): has no units, so anyone can read it, but it is also wrong once the map changes size.

Related concepts

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