How to read map co-ordinates

This page will show you how to read map co-ordinates on the Ordnance Survey map excerpts published throughout this New Forest National Park web site.

OS maps use a grid system that divides the country into squares of 100km x 100km, with each square having a two letter reference. The reference for the New Forest area is SU and these letters prefix the numeric grid reference. Each square is then divided into 100 smaller squares, each one representing 10
These 10km dividing lines are numbered from 1 to 9, starting from the bottom left corner of the 100km square, and so increase left to right ('eastings') and upwards ('northings').

On small scale maps, such as the extracts throughout this web site, these 10km squares are divided again into 1km x 1km squares, with the eastings and northings numbered 01 to 99 through each separate 100km square. In the image below, easting 31 and northing 10 are circled to illustrate this:

Grid references 10 and 31 are circled

How to read 6 digit grid references

Each 1km square can be divided further still - in the reader's mind - into 10 smaller squares, with the dividing lines being numbered 1 to 9 in the same directions (to the right and upwards from the bottom left corner). This smaller 'mental' grid, the red lines in the image below, will pinpoint an exact location within the 1km square.

Ashurst railway station

So to find a place using a given grid reference, simply locate the appropriate easting first (the first two digits of the reference) and then the appropriate northing (the 4th and 5th digits). This intersection will be the bottom left corner of the square that you need to divide up in your mind. Then gauge the distance across and up this square in 1/10ths, according to the 3rd and 6th digits of the reference.

Example from the above excerpt: the grid reference for Ashurst railway station is SU334102.

Greater accuracy can of course be achieved by using an 8 digit grid reference. Here, the distances following the 3rd and 6th digits of a 6 digit reference (the red lines above) are divided again into 1/10ths.
Using the same example, the 8 digit grid reference for Ashurst railway station is SU33381012.

© Copyright information - Both map extracts shown on this page, along with all extracts throughout the New Forest National Park website, are Crown Copyright and have been published under License no.WL8732. The extracts cannot be reproduced without consent.

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