![]() ![]() If you imagine the lines are numbered in the same way as for the hectad, you can count the lines along the bottom of the square until you reach the line forming the left-hand side of the smaller square containing the x and you come to the number 7. To give a more detailed six-figure grid reference, you need to insert a number in the middle of the four-figure grid reference and another one at the end, i.e. ![]() The map margins on the 1:25,000 Ordnance Survey maps are further calibrated into 100-metre divisions, which enables you to imagine the square with the x in it split into 100 smaller squares.īelow is an enlargement of the square ST 3575. The two numbers of that line form the last two numbers of the four-figure grid reference. Next, run your eye up the left-hand, or right-hand, side of the map until you reach the line which forms the bottom of the square in which your record was made. The two numbers of that line form the first numerical part of your four-figure grid reference. Keeping your finger on that square, read the Eastings by running your eye from left to right along the bottom, or top, of the map until you come to a line which, if followed up or down towards the site of your record, represents the left-hand side of the square in which your record was made. To give a four-figure grid reference, first find the square in which your record was made. map are the numbers running from left to right along the top and bottom edges of the map and the Northings are the numbers running from bottom to top at each side of the map. If in doubt, check the legend which will show you a small scale diagram of the squares covered. These letters are found in the corners of the map and, if your map covers more than one square, they will also be printed where one square joins the next on the map. The two-letter code on the Ordnance Survey (O.S.) map you are using forms the first part of your grid reference. British grid references consist of two letters and two to ten numbers. A grid reference refers to the bottom left hand corner of the square which contains the record, not the actual site of the record. These squares are divided into hectads of 10 x 10 km and the hectads are further divided into 1 km squares. Britain is covered by a grid of 100 x 100 km squares, each denoted by a two-letter code e.g. ![]()
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