[PROJ] Gridshift files

[Mladen Mijatovic]

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.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/proj/attachments/20230925/8b13584f/attachment.htm>