I've discovered that the current implementation of RAS Mapper only allows an ESRI Prj file to be read in. It uses the GDAL routines, but in a limited way. I suspect that I should be able to get RAS Mapper to access a custom transformation if I create a dummy ESPG value with the desired parameters in the GDAL files listed in my original email.
Derek On Sun, Apr 3, 2016 at 8:56 PM, Andre Joost <andre+jo...@nurfuerspam.de> wrote: > Am 03.04.2016 um 14:05 schrieb Derek Stuart: > >> Andre: The only Gulshan coordinate system I see with EPSG 4682 is a >> geographic coordinate system. I am using a projected coordinate >> system called BTM. This is a fairly new coordinate system, but it is >> the standard here in Bangladesh. >> >> >> PROJCS["BTM",GEOGCS["GCS_Everest_Bangladesh",DATUM["D_Everest_Bangladesh",SPHEROID["Everest_Adjustment_1937",6377276.345,300.8017]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",-2000000.0],PARAMETER["Central_Meridian",90.0],PARAMETER["Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]] >> >> There is a projected coordinate system called Gulshan 303 Bangladesh >> TM that uses the Gulshan datum, but it has EPSG 3106, not 4682. >> >> >> PROJCS["Gulshan_303_Bangladesh_TM",GEOGCS["GCS_Gulshan_303",DATUM["D_Gulshan_303",SPHEROID["Everest_Adjustment_1937",6377276.345,300.8017]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",90.0],PARAMETER["Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0],AUTHORITY["EPSG",3106]] >> >> This has very similar parameters to BTM, except that Gulshan 303 has >> a false northing of 0 and BTM has -2000000.0. I asked some other >> GIS professionals locally and was told that here isn't a EPSG code >> that matches BTM. Unless I want to reproject my data and work in >> UTM, I don't see a way to avoid adding a custom transformation to >> GDAL. >> > > Your first post did not include information on the projected coordinate > system. Since it has a different false Northing, you really have to put up > a custom CRS. But you have to take the +towgs84 parameter set to shift from > the Everest ellipsoid to WGS84. The WKT definitions you give do not include > that, because the ARCGIS world handles datum transformations separately. > > You can put the WKT definition above in a text file, and run gdalsrsinfo > on that file. It will report: > > +proj=tmerc +lat_0=0 +lon_0=90 +k=0.9996 +x_0=500000 +y_0=-2000000 > +a=6377276.345 +b=6356075.41314024 +units=m +no_defs > > As mentioned above, add the +towgs84 set for Gulshan, which you find in > EPSG:4682: > > +proj=tmerc +lat_0=0 +lon_0=90 +k=0.9996 +x_0=500000 +y_0=-2000000 > +a=6377276.345 +b=6356075.41314024 +towgs84=283.7,735.9,261.1,0,0,0,0 > +units=m +no_defs > > > HTH, > André Joost > > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev > -- Derek
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