Three Peaks Fell Race

[Marvin]

Quiote right Stolly

4 fig GR accurate to 1 Sq Kilometer
6 fig GR Accurate to 100 sq meters
8 fig GR Accurate to 10 sq metres
10 fig GR accurate 1 meter

The letter code denotes a specific area the map covers and can be found on the Key of your OS map. The number grid is repeated every 100 sq kilometers I believe.

Worth noting that if you need to call for help in the UK and you give your location as a 6 fig GR with out the letter you could have a longer wait so always give the letter code.

Sorry to be pedantic (can't resist), but don't you mean that 6 figure GR pins down a location to a 100 M square, i.e. to a square with sides 100M, in other words with an area of 10,000 Sq Metres. And so on for the others.