Wednesday, January 14, 2009

Navigation - The National Grid

The National Grid is a system of squares devised to enable the map makers to have a point of reference, although it is imaginary, to create an index system allowing parts of the country to be identified. This is different from using latitude and longitude.

This National Grid System consists of a frame of 100 kilometre squares laid over the Ordnance Survey Maps of Great Britain. Each 100 km square has a two letter code and is numbered 00 to 99 from West to East and from South to North. It is important to realise that a six figure reference will appear every 100 km and it is essential to quote the two letter prefix will refer to a square (see image).

Beyond knowing that the National Grid System exists and how to order maps using it, the average hill walker and navigator will have very little need of any additional information.

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