Python – Projection Transformations from EPSG 6347 to EPSG 4326

coordinate systemgeopandaspython

I am quite new to GIS and I have a question regarding projection transformations.

I am using GeoPandas to read a map in EPSG 6347 and I use the method to_crs to convert it to EPSG 4326, as documented here.

As far as I understand, the ellipsoid and the datum are entirely specified in the EPSG:

EPSG CRS Datum Ellipsoid
6347 NAD83 2011 GRS80
4326 WSG84 1984 WSG64

and therefore, I thought that there would only be one possible transformation.

The first answer to this question indicates that there are multiple transformations from NAD83 to WSG84. This is also explained in this link. Those transformations are named: NAD_1983_To_WSG_1984_1,…, NAD_1983_To_WSG_1984_8.

Which of those 8 transformations is used by GeoPandas when it converts from EPSG:6347 to EPSG:4326?

Best Answer

Proj version 8.1.1 finds only one conversion between those two codes:

projinfo -s epsg:6347 -t epsg:4326 --spatial-test intersects
Candidate operations found: 1
-------------------------------------
Operation No. 1:

unknown id, Inverse of UTM zone 18N + Ballpark geographic offset from NAD83(2011) to WGS 84, unknown accuracy, World, has ballpark transformation

PROJ string:
+proj=pipeline
  +step +inv +proj=utm +zone=18 +ellps=GRS80
  +step +proj=unitconvert +xy_in=rad +xy_out=deg
  +step +proj=axisswap +order=2,1

WKT2:2019 string:
CONCATENATEDOPERATION["Inverse of UTM zone 18N + Ballpark geographic offset from NAD83(2011) to WGS 84",
    SOURCECRS[
        PROJCRS["NAD83(2011) / UTM zone 18N",
            BASEGEOGCRS["NAD83(2011)",
                DATUM["NAD83 (National Spatial Reference System 2011)",
                    ELLIPSOID["GRS 1980",6378137,298.257222101,
                        LENGTHUNIT["metre",1]]],
                PRIMEM["Greenwich",0,
                    ANGLEUNIT["degree",0.0174532925199433]],
                ID["EPSG",6318]],
            CONVERSION["UTM zone 18N",
                METHOD["Transverse Mercator",
                    ID["EPSG",9807]],
                PARAMETER["Latitude of natural origin",0,
                    ANGLEUNIT["degree",0.0174532925199433],
                    ID["EPSG",8801]],
                PARAMETER["Longitude of natural origin",-75,
                    ANGLEUNIT["degree",0.0174532925199433],
                    ID["EPSG",8802]],
                PARAMETER["Scale factor at natural origin",0.9996,
                    SCALEUNIT["unity",1],
                    ID["EPSG",8805]],
                PARAMETER["False easting",500000,
                    LENGTHUNIT["metre",1],
                    ID["EPSG",8806]],
                PARAMETER["False northing",0,
                    LENGTHUNIT["metre",1],
                    ID["EPSG",8807]]],
            CS[Cartesian,2],
                AXIS["(E)",east,
                    ORDER[1],
                    LENGTHUNIT["metre",1]],
                AXIS["(N)",north,
                    ORDER[2],
                    LENGTHUNIT["metre",1]],
            ID["EPSG",6347]]],
    TARGETCRS[
        GEOGCRS["WGS 84",
            ENSEMBLE["World Geodetic System 1984 ensemble",
                MEMBER["World Geodetic System 1984 (Transit)"],
                MEMBER["World Geodetic System 1984 (G730)"],
                MEMBER["World Geodetic System 1984 (G873)"],
                MEMBER["World Geodetic System 1984 (G1150)"],
                MEMBER["World Geodetic System 1984 (G1674)"],
                MEMBER["World Geodetic System 1984 (G1762)"],
                ELLIPSOID["WGS 84",6378137,298.257223563,
                    LENGTHUNIT["metre",1]],
                ENSEMBLEACCURACY[2.0]],
            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]],
            ID["EPSG",4326]]],
    STEP[
        CONVERSION["Inverse of UTM zone 18N",
            METHOD["Inverse of Transverse Mercator",
                ID["INVERSE(EPSG)",9807]],
            PARAMETER["Latitude of natural origin",0,
                ANGLEUNIT["degree",0.0174532925199433],
                ID["EPSG",8801]],
            PARAMETER["Longitude of natural origin",-75,
                ANGLEUNIT["degree",0.0174532925199433],
                ID["EPSG",8802]],
            PARAMETER["Scale factor at natural origin",0.9996,
                SCALEUNIT["unity",1],
                ID["EPSG",8805]],
            PARAMETER["False easting",500000,
                LENGTHUNIT["metre",1],
                ID["EPSG",8806]],
            PARAMETER["False northing",0,
                LENGTHUNIT["metre",1],
                ID["EPSG",8807]],
            ID["INVERSE(EPSG)",16018]]],
    STEP[
        COORDINATEOPERATION["Ballpark geographic offset from NAD83(2011) to WGS 84",
            SOURCECRS[
                GEOGCRS["NAD83(2011)",
                    DATUM["NAD83 (National Spatial Reference System 2011)",
                        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]],
                    ID["EPSG",6318]]],
            TARGETCRS[
                GEOGCRS["WGS 84",
                    ENSEMBLE["World Geodetic System 1984 ensemble",
                        MEMBER["World Geodetic System 1984 (Transit)"],
                        MEMBER["World Geodetic System 1984 (G730)"],
                        MEMBER["World Geodetic System 1984 (G873)"],
                        MEMBER["World Geodetic System 1984 (G1150)"],
                        MEMBER["World Geodetic System 1984 (G1674)"],
                        MEMBER["World Geodetic System 1984 (G1762)"],
                        ELLIPSOID["WGS 84",6378137,298.257223563,
                            LENGTHUNIT["metre",1]],
                        ENSEMBLEACCURACY[2.0]],
                    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]],
                    ID["EPSG",4326]]],
            METHOD["Geographic2D offsets",
                ID["EPSG",9619]],
            PARAMETER["Latitude offset",0,
                ANGLEUNIT["degree",0.0174532925199433],
                ID["EPSG",8601]],
            PARAMETER["Longitude offset",0,
                ANGLEUNIT["degree",0.0174532925199433],
                ID["EPSG",8602]]]],
    USAGE[
        SCOPE["unknown"],
        AREA["World"],
        BBOX[-90,-180,90,180]]]
Related Question