The map projection

It is customary to define the position of a place or object on the Earth's surface by means of geographical coordinates of latitude and longitude. The framework of parallels and meridians representing the values of latitude and longitude is called a graticule. The diagram shows a part of the graticule covering Great Britain. When features on the curved surface of the Earth are represented on a flat surface, their shape or size will always be subject to distortion in one way or another. Methods for representing these features on paper are known as map projections. Ordnance Survey maps are based on a particular type of map projection called the Transverse Mercator projection which is designed to keep the unavoidable distortions within acceptable limits.

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