Eight Figure Map References
Q. I'm quite familiar with 6 figure map references but how do I give, make or take an eight figure reference?
Ron Knight, Chesterfield
A. A complete grid reference comprises two grid letters (which define a particular 100km x 100km square) plus a 6 figure number (which defines a particular 100m x 100m square within that larger square).
An eight figure grid reference comprises two grid letters (which define a particular 100km x 100km square) plus an 8 figure number (which defines a particular 10m x 10m square within that larger square). So if the six figure grid reference is SD785442 (accurate to 100m) the eight figure grid reference for the same location would be SD78504420 (accurate to 10m).
Ten figure grid references - SD7850044200 are accurate to 1m and usually called GPS Waypoints or GPS Waymarks.
In practice it is pretty difficult to give an accurate eight figure grid reference from a 1:25 000 Scale paper map (e.g. OS Explorer) and impossible to give a 10 figure grid reference (GPS Waypoint). However, the advent of digital mapping has made eight figure grid references more common.
For more information on national grid letters see The National Grid.
For more information on giving a grid reference see Giving a Grid Reference.
For more information on GPS Waypoints and GPS Systems see GPS for Walking and Hiking.
Hope this helps