I am trying to georeference two sheets of the Carte géologique de la France 1/50000 by J. Thierry from 1974/75. It says "Ellipsoid de Clarke" on the map. Unfortunately this is the only information about the CRS I have. The Coordinates used on one of the sheets are in Lat/Lon and as follows: Upper Left: Lon 4°19'2" Lat 48°3'36", Upper Right: Lon 4°40'38" Lat 48°3'36", Lower Left: Lon 4°19'2" Lat 47°52'48", Lower Right: Lon 4°40'38" Lat 47°52'38". Following this information I tried referencing in different Clarke-Ellipsoid based CRS which resulted in the map appearing at the wanted area, but with several hundred meters error. Has anyone ever worked with this map before and knows which CRS they are using?

Edit: So far I used the basic georeferencing tool in QGIS 2.14. I set points in every corner of the sheet and entered the given coordinates (see above) as dd mm ss.ss.

The area is the vicinity of Chatillon-sur-Seine in the Côte d'Or Region. It should be Lambert II or Lambert II etendu, but both do not work.

Additional to the Lon-Values given above there are Lon-Values for the Paris-Meridian. Using them and NTF (Paris) did not solve the problem.

  • 1
    Could you provide a link to the source, please? – mgri Dec 31 '16 at 15:58
  • Depending on the part of France, you're probably dealing with Lambert zone I (EPSG:27571), zone II (27572), zone III (27573) or zone IV (27574). Have you tried these? – ArMoraer Dec 31 '16 at 16:47
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    If mainland France, "Clarke" maps to Clarke IGN in EPSG registry, which means NTF or NTF (Paris). Do you have any coordinates other than lat-lon values? – mkennedy Dec 31 '16 at 19:46
  • there are many crs in France. Please give more detail on your method used to georeferenced the data and check the location. Have you performed a datum transform? What software have you tried ? – radouxju Jan 1 '17 at 17:00

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