Os References on the Yorkshire 3 Peaks Guide
Q. I have just downloaded the Yorkshire 3 Peaks Guide and the grid references given have an extra 2 digits after the eastings and northings. What are these? I have been using OS maps for over 50 years I have not come across this before and find it a little confusing. Or maybe I'm too old now!
A. The 'Grid References' you refer to on The Yorkshire Three Peaks Challenge Walk are GPS Waypoints for the strategic decision points around the walk. These 12 digit references (two letters, 10 numbers) are accurate to 1m* - while standard 8 digit grid references (two letters, 6 numbers) are only accurate to 100m.
*NB. The Waypoint may be accurate to 1m but your GPS Device is typically only accurate to 10 - 25m. Still pretty good though.
Hope this helps . . .