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.
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.
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).
