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Reprojection and grids

Sep 25, 2017 at 3:12 PM
Hello everyone,

I'm trying to reproject coordinates from the "KnownCoordinateSystems.Geographic.World.WGS1984" ProjectionInfo Object to a Lambert conical conform system, defined with a proj4 string.

I need to use the "ntf_rgf93.gsb" grid file, which is provided with DotSpatial in the "Windows Extensions\DotSpatial.Data.Rasters.GdalExtension\gdal\share" folder.

My problem is whether I add "+nadgrids=ntf_r93.gsb" in the proj4 string or not, the transformed coordinates remain the same (and are the gridless ones).

Here are both proj4 strings:
// No grid
+proj=lcc +lat_1=42.16500000000001 +lat_0=42.16500000000001 +lon_0=0 +k_0=0.99994471 +x_0=234.358 +y_0=185861.369 +a=6378249.2 +b=6356515 +towgs84=-168,-60,320,0,0,0,0 +pm=paris +units=m +no_defs

// With grid
+proj=lcc +nadgrids=ntf_r93.gsb +lat_1=42.16500000000001 +lat_0=42.16500000000001 +lon_0=0 +k_0=0.99994471 +x_0=234.358 +y_0=185861.369 +a=6378249.2 +b=6356515 +towgs84=-168,-60,320,0,0,0,0 +pm=paris +units=m +no_defs
I'm obviously missing something. Any ideas? :)