Newbie confused over British grid

[phredde]

Looking at a geocache site it gave a British grid reference of:
00267 72471 (letters omitted)

Working with the local OS map I found that the 6 figure grid reference of the site would be:
002 724

So why the extra numbers? Can someone explain to this elderly newbie what's going on here. Things have changed obviously since I learnt to use the OS in the Forces.

[Lord Darcy]

The extra numbers indicate a greater degree of accuracy. In your example, 002 indicate an 'easting' of 0 x 10km, 0 x 1km and 2 x 100m ... then the extra figures 6 x 10m and 7 x 1m. A similar 'extension' applies to the 'northing' figures.

So the 6 figure grid ref you have worked out from the OS map is correct to the nearest 100 metres - the 10 figure reference is correct to the nearest metre.

Hope that helps.

Paul

[Graculus]

You can set your GPS to the OS grid system if you want to but be careful when switching from OS grid to Lat and Long as you can end up with the map datum wrong and you'll find you're some 100 yards (meters) out. The GPS shows the OSGB reference as 10 digits.

For practical purposes when geocaching it's best to leave your GPS on Lat/Long rather than OS GB as all coordinates on the cache page use this format and it's easier.

Chris (MrB)
UK Geocaching Information & Resources website www.follow-the-arrow.co.uk (http://www.follow-the-arrow.co.uk)

[phredde]

Thank you for the replies and the information. It's all changed since I first used an OS map.
I guess I'll have to catch up. But thanks again.