NTF to RGF93

The NTF to RGF93 transformation converts coordinates from NTF (Nouvelle Triangulation de la France) to RGF93 (Réseau Géodesique Français) using a grid file defined by IGN (the French National Geographical Institute). This transformation uses bilinear interpolation.

The file is named gr3df97a.txt, and it can be downloaded from our website:

https://www.bluemarblegeo.com/geographic-calculator-download/

The default grid file assumes a Greenwich prime meridian.

NOTE: The definition of datum transformations using this method includes parameters specifying the required grid files. If the system cannot find the specified file, the shift will be marked unusable in the Datasource and can not be selected for use.