How to use grid references
A grid reference is a short code that pinpoints a place on a map. With six numbers you can describe a spot to within 100 metres, anywhere in Great Britain.
The grid
Maps like Ordnance Survey’s are covered in blue grid lines 1 kilometre apart. The lines running up and down are numbered along the bottom and top; these numbers are called eastings because they increase as you go east. The lines running across are numbered up the sides; these are northings, increasing as you go north. Contour’s map has the same 1 kilometre grid.
Four-figure references: which square
To name a square, take the easting of the line on its left, then the northing of the line along its bottom. In the example below, the highlighted square is 34 72, written 3472.
The classic way to remember the order is “along the corridor, then up the stairs”: go along first (eastings), then up (northings).
Six-figure references: where in the square
Imagine the square divided into ten strips each way. Count how many tenths across the point is, and add that digit after the easting; then count how many tenths up, and add it after the northing.
- Along the corridor: the point is in the square starting at easting 34, and 6 tenths across. That gives 346.
- Up the stairs: it’s in the square starting at northing 72, and 3 tenths up. That gives 723.
The full reference is 346 723. Each tenth of a 1 kilometre square is 100 metres, so a six-figure reference finds a place to within 100 metres.
Grid references in Contour
When you place your guess, Contour shows its six-figure reference, and after you lock in it tells you the reference where you were really standing. Comparing the two is a quick way to practise: if your guess was 346 723 and you were at 349 721, you were 3 tenths too far west and 2 tenths too far north, about 300 metres off.