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Thursday, March 3, 2011
A large scale map can show a relatively high level of detail, whereas a small scale map contains more information in relation to its size. The scale of a map is expressed as the ratio between the size of the map and the size of the corresponding area on the ground. This can be expressed as a simple ratio, for example 1:100, where one unit on a map is equal to 100 of the same units on the ground. Alternatively, the ratio may be expressed using different units, for example 1cm: 1km, in which one centimeter on the map represents one kilometer on the ground. Many maps also show scale in the form of a scale bar which can be used to calculate any distance on the map. The scale dictates the level of detail shown by the map. Because maps are smaller than the areas they represent, symbols are used to indicate the features on the ground. Many symbols do not resemble the things the things they represent and so they are often explained in a key.