Grid References

How to give a national grid reference to the nearest 100 metres
SAMPLE POINT: Slaper Leys (in the map below).

1. Read the letters identifying the the 100000m square from the corner of the map SE

2. FIRST QUOTE EASTINGS - Find the first verticle grid line to the LEFT of the point and read the LARGE numbers labelling the line either at the top or bottom of the line 02
Divide the square in to ten by eye and estimate the tenths from the grid line to the point 3

3. AND THEN QUOTE THE NORTHINGS - Find the first horizontal grid line BELOW the point and read the LARGE numbers labelling the line either in the left or right of the margin 54
Divide the square in to ten by eye and estimate the tenths from the grid line to the point 5

SAMPLE REFERENCE is SE 023 545 The letters are often left out when working locally.

GRID REFERENCES (GR)
Ships navigators use lines of longitude and latitude to identify locations on a chart. This is not possible on maps drawn to a large scale because the lines of longitude and latitude are too far apart. British maps are divided into squares using a system of vertical and horizontal lines known as grid lines: hence the term 'grid squares (GS)'.
The OS 1:50,000 maps have grid lines spaced one kilometre apart and numbered 1 to 100. These grid lines are based on a National Grid system in which the whole area of the British Isles is divided into squares with 100 kilometre sides and with a two letter reference for each square. Look now at sheet 99(or any other but the letters will be different) and you will see that the map contains part of square SE. (These large letters can be seen on the top and bottom corners of the map) The letters are not normally used when referring to a map of the 1:50,000 scale, as one sheet does not exceed 100 kilometres square and a GR can only refer to one part of the map.
In order to give a GR, think of each vertical line as a line of longitude and each horizontal line as a line of latitude. These are known as Eastings and Northings respectively, and are always given in that order. If you look at the box at the bottom of the legend to Map Sheet 99 (see also box (j) on the maginal information page) it tells you how to give a GR.
Note that a Grid Square (GS) is given as a 4 figure GR - this covers an area 1000 m square. A location is normally given as a 6 figure GR - giving an accuracy to the nearest 100 m. To be more accurate, it is possible to divide the square further to produce an 8 figure GR - giving greater accuracy to the nearest 10 m.
How to give a national grid reference to the nearest 100 metres SAMPLE POINT: Slaper Leys (in the map below). 1. Read the letters identifying the the 100000m square from the corner of the map SE 2. FIRST QUOTE EASTINGS - Find the first verticle grid line to the LEFT of the point and read the LARGE numbers labelling the line either at the top or bottom of the line 02 Divide the square in to ten by eye and estimate the tenths from the grid line to the point 3 3. AND THEN QUOTE THE NORTHINGS - Find the first horizontal grid line BELOW the point and read the LARGE numbers labelling the line either in the left or right of the margin 54 Divide the square in to ten by eye and estimate the tenths from the grid line to the point 5 SAMPLE REFERENCE is SE 023 545 The letters are often left out when working locally.

EXAMPLES
You can confirm your ability to read GRs by looking at the following examples:
a.Grid Squares.	(1) Common Farm is in 0351.
	(2) Hutton is in 0253.
	(3) Sunderlandwick Hall is in 0156.
b. Six Figure Grid References	(1) Slayper Leys is at 023545.
	(2) Clayfloor Farm is at 034533.
	(3) Skern Grange is at 041550.
c. Eight Figure Grid References.	(1) Track/Road Junction at 01875392.
	(2) Church at 02425328.
	(3) Clayfloor Farm is at 03385327