I am trying to transform coordinates of points in Nord Sahara 1959 Voirol Unifie Nord into UTM31N WGS84. I can only find Nord Sahara 1960 Voirol Unifie Nord in Franson. I have tried doing the conversion with this Datum but the points are about 1000m off in the NW-SE direction. I have ArcGIS 10.0 and 10.1 and can recover the datum I need eg Nord Sahara 1959 Voirol Unifie Nord from the coordinate file in 10.0 but I don't see how to import it into Franson since it is asking for a .ctxml file. Is there anyway to get from the Esri .prj file to an .ctxml file? And why is the Nord Sahara 1960 Voirol Unifie Nord transformation so far off? Thanks for your answers.