Geocentric translation by Grid Interpolation (IGN)
gr3df97a.txt
May be emulated using NTv2 method - see tfm code 15958. Also used to transform between NTF and later realizations of RGF93.
Institut Geographique National (IGN) document NTG_88.pdf, "Grille de parametres de transformation de coordonnees". http://www.ign.fr
2022-01-24
Definition: OGC Well Known Text 2 (2019)
BOUNDCRS[ SOURCECRS[ GEOGCRS["NTF", DATUM["Nouvelle Triangulation Francaise", ELLIPSOID["Clarke 1880 (IGN)",6378249.2,293.466021293627, LENGTHUNIT["metre",1]]], PRIMEM["Greenwich",0, ANGLEUNIT["degree",0.0174532925199433]], CS[ellipsoidal,2], AXIS["geodetic latitude (Lat)",north, ORDER[1], ANGLEUNIT["degree",0.0174532925199433]], AXIS["geodetic longitude (Lon)",east, ORDER[2], ANGLEUNIT["degree",0.0174532925199433]], USAGE[ SCOPE["Geodesy."], AREA["France - onshore - mainland and Corsica."], BBOX[41.31,-4.87,51.14,9.63]], ID["EPSG",4275]]], TARGETCRS[ GEOGCRS["RGF93 v1", DATUM["Reseau Geodesique Francais 1993 v1", ELLIPSOID["GRS 1980",6378137,298.257222101, LENGTHUNIT["metre",1]]], PRIMEM["Greenwich",0, ANGLEUNIT["degree",0.0174532925199433]], CS[ellipsoidal,2], AXIS["geodetic latitude (Lat)",north, ORDER[1], ANGLEUNIT["degree",0.0174532925199433]], AXIS["geodetic longitude (Lon)",east, ORDER[2], ANGLEUNIT["degree",0.0174532925199433]], USAGE[ SCOPE["Horizontal component of 3D system."], AREA["France - onshore and offshore, mainland and Corsica (France métropolitaine including Corsica)."], BBOX[41.15,-9.86,51.56,10.38]], ID["EPSG",4171]]], ABRIDGEDTRANSFORMATION["NTF to RGF93 v1 (1)", METHOD["Geocentric translation by Grid Interpolation (IGN)", ID["EPSG",1087]], PARAMETERFILE["Geocentric translation file","gr3df97a.txt"], USAGE[ SCOPE["Transformation of coordinates at 1m level of accuracy."], AREA["France - onshore - mainland and Corsica."], BBOX[41.31,-4.87,51.14,9.63]], ID["EPSG",9327], REMARK["May be emulated using NTv2 method - see tfm code 15958. Also used to transform between NTF and later realizations of RGF93."]]]
Definition: JSON
{ "$schema": "https://proj.org/schemas/v0.7/projjson.schema.json", "type": "BoundCRS", "source_crs": { "type": "GeographicCRS", "name": "NTF", "datum": { "type": "GeodeticReferenceFrame", "name": "Nouvelle Triangulation Francaise", "ellipsoid": { "name": "Clarke 1880 (IGN)", "semi_major_axis": 6378249.2, "semi_minor_axis": 6356515 } }, "coordinate_system": { "subtype": "ellipsoidal", "axis": [ { "name": "Geodetic latitude", "abbreviation": "Lat", "direction": "north", "unit": "degree" }, { "name": "Geodetic longitude", "abbreviation": "Lon", "direction": "east", "unit": "degree" } ] }, "id": { "authority": "EPSG", "code": 4275 } }, "target_crs": { "type": "GeographicCRS", "name": "RGF93 v1", "datum": { "type": "GeodeticReferenceFrame", "name": "Reseau Geodesique Francais 1993 v1", "ellipsoid": { "name": "GRS 1980", "semi_major_axis": 6378137, "inverse_flattening": 298.257222101 } }, "coordinate_system": { "subtype": "ellipsoidal", "axis": [ { "name": "Geodetic latitude", "abbreviation": "Lat", "direction": "north", "unit": "degree" }, { "name": "Geodetic longitude", "abbreviation": "Lon", "direction": "east", "unit": "degree" } ] }, "id": { "authority": "EPSG", "code": 4171 } }, "transformation": { "name": "NTF to RGF93 v1 (1)", "method": { "name": "Geocentric translation by Grid Interpolation (IGN)", "id": { "authority": "EPSG", "code": 1087 } }, "parameters": [ { "name": "Geocentric translation file", "value": "gr3df97a.txt", "id": { "authority": "EPSG", "code": 8727 } } ], "id": { "authority": "EPSG", "code": 9327 } } }
Definition: Mapnik
<?xml version="1.0" encoding="utf-8"?> <Map srs="+proj=longlat +ellps=clrk80ign +no_defs +type=crs"> <Layer srs="+proj=longlat +ellps=clrk80ign +no_defs +type=crs"> </Layer> </Map>