EPSG:9891

COORDINATEOPERATION["ETRS89-FRA [RGF93 v2b] to NTF (2)",
    VERSION["ESRI-Fra 1m emulation"],
    SOURCECRS[
        GEOGCRS["ETRS89-FRA [RGF93 v2b]",
            DATUM["Reseau Geodesique Francais 1993 v2b",
                ELLIPSOID["GRS 1980",6378137,298.257222101,
                    LENGTHUNIT["metre",1]],
                ANCHOREPOCH[2019]],
            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",9782]]],
    TARGETCRS[
        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]],
            ID["EPSG",4275]]],
    METHOD["NTv2",
        ID["EPSG",9615]],
    PARAMETERFILE["Latitude and longitude difference file","rgf93_ntf.gsb"],
    OPERATIONACCURACY[1.0],
    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",9891],
    REMARK["Emulation of transformation NTF to ETRS89-FRA [RGF93 v2b] (1), code 9889. Note that grid file parameters are of opposite sign. Parameter file is from ETRS89-FRA [RGF93 v1] to NTF (code 15958), assuming that ETRS89-FRA [RGF93 v1] is equivalent to ETRS89-FRA [RGF93 v2b] within the accuracy of the CT."]]

proj4.defs("EPSG:9891","+proj=pipeline +step +proj=axisswap +order=2,1 +step +proj=unitconvert +xy_in=deg +xy_out=rad +step +inv +proj=hgridshift +grids=fr_ign_ntf_r93.tif +step +proj=unitconvert +xy_in=rad +xy_out=deg +step +proj=axisswap +order=2,1");

{
    "$schema": "https://proj.org/schemas/v0.7/projjson.schema.json",
    "type": "Transformation",
    "name": "ETRS89-FRA [RGF93 v2b] to NTF (2)",
    "source_crs": {
        "type": "GeographicCRS",
        "name": "ETRS89-FRA [RGF93 v2b]",
        "datum": {
            "type": "GeodeticReferenceFrame",
            "name": "Reseau Geodesique Francais 1993 v2b",
            "anchor_epoch": 2019,
            "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": 9782
        },
        "remarks": "Replaces ETRS89-FRA [RGF93 v2] (CRS code 9777) from 2021-01-05. See CRS code 9784 for alternate system with axes reversed used by IGN for GIS purposes."
    },
    "target_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
        }
    },
    "method": {
        "name": "NTv2",
        "id": {
            "authority": "EPSG",
            "code": 9615
        }
    },
    "parameters": [
        {
            "name": "Latitude and longitude difference file",
            "value": "rgf93_ntf.gsb",
            "id": {
                "authority": "EPSG",
                "code": 8656
            }
        }
    ],
    "accuracy": "1.0",
    "scope": "Transformation of coordinates at 1m level of accuracy.",
    "area": "France - onshore - mainland and Corsica.",
    "bbox": {
        "south_latitude": 41.31,
        "west_longitude": -4.87,
        "north_latitude": 51.14,
        "east_longitude": 9.63
    },
    "id": {
        "authority": "EPSG",
        "code": 9891
    },
    "remarks": "Emulation of transformation NTF to ETRS89-FRA [RGF93 v2b] (1), code 9889. Note that grid file parameters are of opposite sign. Parameter file is from ETRS89-FRA [RGF93 v1] to NTF (code 15958), assuming that ETRS89-FRA [RGF93 v1] is equivalent to ETRS89-FRA [RGF93 v2b] within the accuracy of the CT."
}

<?xml version="1.0" encoding="utf-8"?>
<Map srs="+proj=pipeline +step +proj=axisswap +order=2,1 +step +proj=unitconvert +xy_in=deg +xy_out=rad +step +inv +proj=hgridshift +grids=fr_ign_ntf_r93.tif +step +proj=unitconvert +xy_in=rad +xy_out=deg +step +proj=axisswap +order=2,1">
	<Layer srs="+proj=pipeline +step +proj=axisswap +order=2,1 +step +proj=unitconvert +xy_in=deg +xy_out=rad +step +inv +proj=hgridshift +grids=fr_ign_ntf_r93.tif +step +proj=unitconvert +xy_in=rad +xy_out=deg +step +proj=axisswap +order=2,1">
	</Layer>
</Map>

INSERT into spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext) values ( 9891, 'EPSG', 9891, '+proj=pipeline +step +proj=axisswap +order=2,1 +step +proj=unitconvert +xy_in=deg +xy_out=rad +step +inv +proj=hgridshift +grids=fr_ign_ntf_r93.tif +step +proj=unitconvert +xy_in=rad +xy_out=deg +step +proj=axisswap +order=2,1', 'None');