The numbers going across the map from left to right are called eastings, and go up in value eastwards, and the numbers going up the map from bottom to top are called northings, because they go up in a northward direction.
There are two main types of grid reference:
- four-figure grid reference, such as ‘19 45’, indicates a 1 km by 1 km square on the map; and
- six-figure grid reference, such as ‘192 454’, indicates a 100 m by 100 m square on the map.
- eight-figure grid reference, such as ‘1926 4548’, indicates a 10 m by 10 m square on the map; and
- ten-figure grid reference, such as ‘19267 45487’, indicates a 1 m by 1 m square on the map
Four-figure grid references
When giving a four-figure grid reference, you should always give the eastings number first and the northings number second, very much like when giving the reading of a graph in school, where you give the x coordinate first followed by the y.
An easy way to remember this is that to get the first number, you go along the corridor (horizontal, x axis, eastings) and then up the stairs (vertical, y axis, northings).
For example, the number 2 in the diagram below is square 19 across and square 45 up and therefore, the four-figure grid reference is ‘1945’.
The numbered squares on the diagram above have the following four-figure grid references:
1 = 18 45
2 = 19 45
3 = 18 44
4 = 19 44
Six-figure map references
To get the six-figure grid reference, you have to imagine that the four-figure square is further divided up into tenths.
In the example below, the grey box is in the four-figure grid reference square ‘18 44’, but more accurately it is 7 tenths across and 8 tenths up within that larger grid square, therefore the six-figure map reference is ‘187 448’.
The shapes on the diagram above have the following six-figure grid references:
Grey square – 187 448
Red dot – 185 443
To be sure there is no doubt or confusion about which National Grid you’re referring, when you quote the six-figure grid reference you should put the two letters of the area you are in before the numbers.
For example, you may be at grid reference ‘509 582’ in south-west Scotland. The complete grid reference you should quote would be ‘NX 509 582’ (without the letters the numeric reference would be repeated in every 100 km square).
Using compass romer lines
The romer lines marked on the base plate of most compasses can help you to get a more accurate grid reference. You choose the scale of the map you’re using and then move the compass base plate over the map to show the tenths within a map square. This is more accurate than guessing the tenth gradations within a square
