Kent and Medway Biological Records Centre

Grid References

Grid Reference Guide

3. Standard 6-figure Grid

A 6-Figure Grid Reference is generally used as the standard and refers to a further subdividing grid. It is the predominant grid reference used both in biological recording and given as a point on an Ordnance Survey (OS) map to define a location, such as a meeting point.

If the highlighted grid square in

figure 5

(TQ7356) was further subdivided into 100 equal squares, each square would measure 100m x 100m and would allow you to give a relatively accurate grid reference for a point, or at least give someone else a reasonable chance of finding that point again with the aid of an OS map, especially with further site information.

Figure 6Figure 6; Locating a point within TQ7356
However, to draw these lines on a map would make it very difficult to see any other details. Consequently, you have to judge for yourself approximately how many tenths along and up the square the point is. For example, if we take the highlighted TQ7356 square above, we can mentally subdivide into 10 along the bottom and up the side, as below.

We then need to locate a point within the square that we want to find a grid reference for, as below (X marks the spot as always)

We can then see that the 'X' is approximately 6 tenths along the bottom and 9 tenths up the side, as below.

You now have the information you require to give a complete 6-figure grid reference, using the following method, again always reading west-east first followed by south-north (which is sometimes remembered by the phrase 'along the hall and up the stairs').
Figure 9The 6-figure Grid Reference

4.aAccuracy of Different Grid References

As mentioned above, different grid references have different accuracies. In general, the longer the grid reference, the more accurate the reference. The most often used ones are as follows:
TQAnywhere within the 100km x 100km square
TQ11Anywhere within the 10km x 10km square
TQ1212Anywhere within the 1km x 1km square
TQ123123Anywhere within the 100m x 100m square
TQ12341234Anywhere within the 10m x 10m square *
TQ1234512345Anywhere within the 1m x 1m square *


* = It should be noted that these grid references are only possible to obtain with the use of a Global Positioning System unit (GPS).

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