How do I set my GPS for walking in France
Q. I wish to use my Garmin Etrex Vista in France, I have GPS compatible 1:25000 maps. How do I change the setup from UK Ordnance Survey to the French grid system?
William Milne, Worksop
A. You do not say which maps you have - but if they are the Blue IGN Series then use the buttons on the sides of your GPS unit and navigate to the 'SETUP' screen. Scroll down to 'UNITS' and then enter:
Position Format: UTM/UPS
Map Datum: WGS84
This page GPS Datum for Walking in France includes a bit more information and links to all things GPS.
Hope this helps