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I've been digging into the WKT format definition found here:WKT Format with the aim of defining a PRJ with two chained affine transforms to go from a known projected system to a local grid.

I've been unable to generate any kind of PRJ that works with packages like GDAL and was wondering if anyone has any kind of example file that uses the CONCAT_MT entity alongside a standard projection?

Even getting any working implementation of Concat_MT with GDAL at all would be a start, I've tried a few variations like the one below with no success.

PROJCS[
    "WGS84 like system to local ground coordinates",
    GEOGCS[
        "Unknown datum based upon the WGS 84 ellipsoid",
        DATUM[
            "Not_specified_based_on_WGS_84_ellipsoid",
            SPHEROID[
                "WGS 84",6378137,298.257223563,
                AUTHORITY["EPSG","7030"]
            ],
            AUTHORITY["EPSG","6030"]
        ],
        PRIMEM[
            "Greenwich",0,
            AUTHORITY["EPSG","8901"]
        ],
        UNIT[
            "degree",0.0174532925199433,
            AUTHORITY["EPSG","9122"]
        ],
        AUTHORITY["EPSG","4030"]
    ],
    CONCAT_MT[
      PARAM_MT["Mercator_2SP",
        PARAMETER["semi_major",6370997.0],
        PARAMETER["semi_minor",6370997.0],
        PARAMETER["central_meridian",180.0],
        PARAMETER["false_easting",-500000.0],
        PARAMETER["false_northing",-1000000.0],
        PARAMETER["standard parallel 1",60.0]],
        PARAM_MT["Affine",
        PARAMETER["num_row",3],
        PARAMETER["num_col",3],
        PARAMETER["elt_0_1",1],
        PARAMETER["elt_0_2",2],
        PARAMETER["elt 1 2",3]]]
    UNIT["metre",1,AUTHORITY["EPSG","9001"]],
    AXIS["Easting",EAST],
    AXIS["Northing",NORTH]
]

Does anyone have a working example PRJ with multiple affine transformations applied to a projected system?

  • 1
    I don't know if GDAL has ever supported these kind of WKT. Do you get any helpful debug output when you have CPL_DEBUG=ON in your environment when you try gdalsrsinfo on the WKT in a file? – Howard Butler Jul 31 '17 at 2:50

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