Mladen, See this thread where Even suggests how to use arbitrary grid shift in WKT CRS definition. https://lists.osgeo.org/pipermail/proj/2019-December/009143.html
You would need to use ABRIDGEDTRANSFORMATION. https://docs.ogc.org/is/18-010r7/18-010r7.html#151 Sincerely, Erixen ________________________________ From: PROJ <[email protected]> on behalf of Mladen Mijatovic via PROJ <[email protected]> Sent: Monday, September 25, 2023 5:56 AM To: [email protected] <[email protected]> Subject: [PROJ] Gridshift files Dear, We are trying to substitute old Proj 5.1 in our project and use new Proj 9.2.1. When crs is defind with proj4string or wkt, we do not have issue with transforming coordinates from/to EPSG:4326, except when we are using grid files e.g. +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +datum=OSGB36 +units=m +ellps=airy +no_defs +nadgrids=OSTN15_NTv2_OSGBtoETRS.gsb +type=crs PROJCS["ED50 / 3-degree Gauss-Kruger zone 10", GEOGCS["ED50", DATUM["European_Datum_1950", SPHEROID["International 1924",6378388,297], EXTENSION["PROJ4_GRIDS","SPED2ETV2.gsb"]], PRIMEM["Greenwich",0, AUTHORITY["EPSG","8901"]], UNIT["degree",0.0174532925199433, AUTHORITY["EPSG","9122"]], AUTHORITY["EPSG","4230"]], PROJECTION["Transverse_Mercator"], PARAMETER["latitude_of_origin",0], PARAMETER["central_meridian",30], PARAMETER["scale_factor",1], PARAMETER["false_easting",10500000], PARAMETER["false_northing",0], UNIT["metre",1, AUTHORITY["EPSG","9001"]], AUTHORITY["EPSG","2207"]] Conversion fails with (HUGE_VAL, HUGE_VAL) coordinates. If we allow user to define crs by proj4string or wkt and use gridshift files: - How proj4string/wkt need to looks like? - What c++ functions we need to call to get these coordinates converted without any errors? Best regards, Mladen.
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