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Help on grid references

Entering a grid reference directly is often the most straightforward way to tell us where your site is. Ideally we would like you to give the reference of the 1 km square (1 km x 1 km) where your site is located or, for large sites, the 1 km square closest to the centre of the site. If your site is very large or there is uncertainty about its precise location (for example within a large expanse of open moorland) please give a 10 km square (10 km x 10 km) reference.

To work out a grid reference, first determine the letter code for the 100 km square where your square is located. For 1:50,000 Ordnance Survey maps this is shown on the map key. 100 km squares in Britain are designated by two letters, while in Ireland they are designated by a single letter. Select the appropriate letter code from the drop down menu eg TL.

Use the grid lines on the map to read off the reference for the bottom left hand corner of the square of interest. First read the easting from the top or bottom of the map and then read the northing from the side of the map. For a 1 km square each of these numbers will have two digits, giving four in total, while for a 10 km square each number will have a single digit, giving two in total. Include leading zeros if appropriate.

When you press the "submit site details" button, the grid reference and county that you have entered will be checked against each other for inputting errors. If a mistake is detected then you will given a chance to correct it.