French Paper Maps marked GPS compatiable Coord system ?

[TonyIshUk]

I have some French paper tourist maps (Inst Geographique Nat) 1:25k scale. Which are marked as “GPS compatible” The maps have several coordinate systems on them which do not to seem to relate to each other?

1) GPS coordinates seem to be the main system on which the 1 K grid lines are based.
2) There is a second coordinate system which on the northings have the same coordinate but displaced to the south by about 100m. The eastings system is the same but is displaced by 2200 metres
3) The map also has traditional longitude and latitude in deg, min, secs and decimal gr system. But it is difficult to use because the information is shown on the edge of the map and not shown as a grid.

Can anyone tell me which coordinate system I should be using with the maps? I use Navio PDA software which gives me a choice of WGS84 in various guises of deg, mm, sec or decimal equivalents.

The software also gives a choice of UTM (WGS84) and UTM (International) which I imagine may be used.

Any advice would be appreciated.

Many thanks

Tony Ish UK

[lbendlin]

All you can use is Lon/Lat - that's basically WGS84. If they are only shown at the edges then you'll have to try and place the calibration points there too and see how accurate it gets.

If the area isn't too big then the lines may actually be nearly straight.
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Lutz

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[TonyIshUk]

Thanks, I'll investigate and let you know how I get on.

[TonyIshUk]

Just to add that I have some "rough" fixes taken off the Google world map site. I'll see what happens when I get to France and match the readings.

[kartracer]

If I recall correctly from a visit to France in April, WGS84 and Lat/Lon in DD.ddddd should match up with the French GPS compatible map grid.
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Kam

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