To calculate a four-figure grid reference 20 25 26 27 28 29 1 19 19 20
To get the four-figure grid reference number for Newcourt, Co. Wicklow, in this OS map fragment:
1 2 3
18 2 17 17
What is the four-figure grid reference for the Martello Tower?
16
25 26 27 3
28 2916 Six-Figure Grid References
Six-figure grid references are used to give the exact location of a feature within a grid square.
To get a six-figure grid reference, we must imagine that the distance between each pair of Eastings and between each pair of Northings is divided by ten, as in decimal measurement. This will enable us to give a third figure for both the Easting and Northing readings.
To calculate a six-figure grid reference 53 2 3 B 1 10 52 78 84
0 1 2 3 4 5 6 7 8 9 10 85
4
0 1 2 3 4 5 6 7 8 9
To get the six-figure grid reference number for the letter B in this image:
1 2 3 4
First identify the sub-zone the OS map is taken from (the letter). In this case the sub-zone is ‘T’.
Identify what square the letter B is in using four-figure grid referencing: T 84 52
Now count the number of squares east of 84 to find the letter B. In this example, it is 2 lines east of 84.
Now count the number of lines north of 52 to find the letter B. In this example, it is 8 lines north of 52
If we add these new figures to our four-figure grid reference, we get: T 842 528
18
Start by giving the sub-zone letter located on the map.
Next, give the two-digit number of the Easting on the left side of the square.
Then give the two-digit number of the Northing on the bottom side of the square.
Therefore, the four-figure grid reference for Newcourt is: O 27 17.
