<P> Grid north is a navigational term referring to the direction northwards along the grid lines of a map projection . It is contrasted with true north (the direction of the North Pole) and magnetic north (the direction in which a compass needle points). Many topographic maps, including those of the United States Geological Survey and Great Britain's Ordnance Survey, indicate the difference between grid north, true north, and magnetic north . </P> <P> The grid lines on Ordnance Survey maps divide the UK into one - kilometre squares, east of an imaginary zero point in the Atlantic Ocean, west of Cornwall . The grid lines point to a Grid North, varying slightly from True North . This variation is smallest along the central meridian (north - south line) of the map, and greatest at the map edges . The difference between grid north and true north is very small and can be ignored for most navigation purposes . The difference exists because the correspondence between a flat map and the round Earth is necessarily imperfect . </P>

Difference between true north magnetic north and grid north
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