National Survey Grid Reference
A National Survey Grid Reference is a technique of identifying any exact location in the UK by using geographical co-ordinates based on the National Grid.
The two values which make up an NSGR are known as Northings (generally depicted on maps as vertical lines) and Eastings (generally depicted on maps as horizontal lines). Full NSGR co-ordinates, with six figures for both the Northing and the Easting, are accurate to within one metre. For further information on the National Grid, refer to The Ordanance Survey website.