A six-figure Grid Reference is generally used as the standard for biological recording, giving a location to within 100m. Landranger maps from Ordnance Survey which use a scale of 1:50,000 (or 2cm to 1km) are very useful. The 100km square(s) covered by the map have letter codes such as TF, TG, TL or TM: these are clearly printed in each corner. Each 100km square is further subdivided into one hundred 1km squares which are formed from blue grid lines, spaced 1km apart. The eastings are marked along the top and bottom edges of each map, and the northings down the sides. The convention for a six-figure Grid Reference is [2 grid letters] [3 figures easting] [ 3 figures northing]. For example, the six figure grid reference for Horning church is TG343174.
Please note, when submitting a record it is very useful to include a location name or description alongside the grid reference. This allows us to double check that the grid reference is correct.