A grid of squares helps the map-reader to locate a place. The horizontal lines crossing the map from one side to the other are called northings. They are numbered - the numbers increase to the north. The vertical lines crossing the map from top to bottom are called eastings as the numbers increase in an easterly direction.
Things to remember:
- On an OS map each grid square is 1 km x 1 km or 1 sq km.
- When you give a grid reference, always give the easting first: "Along the corridor and up the stairs".
Four-figure grid references can be used to pinpoint a location to within a square measuring 1 sq km. To find the number of the square:
- Start at the left-hand side of the map and go east until you get to the easting crossing through the bottom-left-hand corner of the square you want. Write this number down.
- Move north until you get to the northing crossing the bottom-left-hand corner of the square you want. Look at the number of this grid line and add it to the two-digit number you already have. This is your four-figure grid reference.
In this case, the tourist information office is in grid square 4733.
Sometimes it is necessary to be even more accurate. In this case you can imagine that each grid is divided into 100 tiny squares. The distance between one grid line and the next is divided into tenths.
- First, find the four-figure grid reference but leave a space after the first two digits. When you get to the easting at the left-hand side of the grid square you want, keep moving east and estimate or measure how many tenths across your symbol lies. Write this number after the first two digits.
- Next, move north from the bottom-left-hand corner of your grid square and estimate how many tenths your symbol is from this point. Put them together to create a six figure grid reference.
In this instance, the tourist information office is located at 476334.