Getting a grid reference

The British National Grid Reference System is commonly used in Britain and differs from the longitude and latitude system, which is used by many other countries. It is a very easy and accurate system to use.

UK 100km grid

To arrive at a unique Ordnance Survey map reference, Great Britain is first divided into a series of 500km squares starting at the Southwest corner of the country. Each of these 500km squares is allocated a single reference letter (S, T, N, H or O).

Each 500km square is then subdivided into 25 squares, 100km by 100km. Each of these 100km squares is allocated a reference letter (A to Z, omitting I, starting with A in the north-west corner of the parent 500km square). 

In this way each 100km square can be referred to by a unique 2 letter reference, with the first letter referring to the parent 500km square, and the second letter referring to a particular 100km square within it.

The 2 letter reference for the area where the Merseyside BioBank office is based is SJ.

BioBank location map (grid)

Look at the map above and find the Merseyside BioBank Office (a red star).

A four-figure grid reference will give the actual square the feature is in, therefore the four-figure reference for the BioBank Office is SJ 41 90.

In reality, this is a large area so to get a more accurate reference we subdivide it further to a six- figure reference:-

This six-figure reference is gained from using 'imaginary' grid lines further dividing the grid square into 10, both from "west to east" and then from "south to north".

Therefore the six-figure reference for the Merseyside BioBank Office is SJ 418 900 (where the 8 & 0 have been estimated).