What is a grid reference?

All Ordnance Survey maps are covered in a series of blue grid lines. These grid lines help you pinpoint an exact location anywhere on the map by giving a unique number known as a grid reference. The vertical lines (the ones that go up and down) are called eastings, as they go up in value as you travel east on the map. The horizontal lines (or the ones that go across) are called northings, since they go up in value as you travel north on the map.

If you want to pinpoint an exact place on a map, such as your own house, you will need to use a six-figure grid reference, which you get by putting together the numbers of the easting and northing that cross in its bottom left-hand corner.

Grid references are easy if you can remember that you always have to go along the corridor before you go up the stairs.

Many helicopter pilots rely on an accurate grid reference in order to land at a precise location, and the emergency services often find rural locations much faster if they are given a similarly accurate reference.

More information on understanding maps.

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