[Gdal-dev] proj4/wkt --> epsg

[Mateusz Loskot]

Shoaib Burq wrote:
> Hi, I was just wondering if there is a way to programatically convert
> proj4 or wkt to and EPSG code in OSR?

One of possibilities I see is to import SRS to OGRSpatialReference:

char* pszWkt = "..."; // put here your SRS WKT definition

OGRSpatialReference srs;
srs.exportToWkt( &pszWkt );

const char* pszTarget = 0;
const char* pszAuthName = 0;
const char* pszAuthCode = 0;

if (srs.IsProjected())
   pszTarget = "PROJCS";
else
   pszTarget = "GEOGCS";

pszAuthName = srs.GetAuthorityName( pszTarget );
if( NULL != pszAuthName )
{
   if( EQUAL( pszAuthName, "EPSG" ) )
   {
      pszAuthCode = srs.GetAuthorityCode( pszTarget );
      if( NULL != pszAuthCode )
      {
           // XXXXXXXXXXXXXXXXXXXXXXXXXXXXX
           // Here is the epsg code
           int epsg = atoi(pszAuthCode);
      }
   }
}

Similarly, you should be able to import SRS from PROJ.4 definition using
OGRSpatialReference::importFromProj4().

I've not compiled this code above, it is a copy&paste with small
modifications from ogr/ogr2gmlgeometry.cpp file, starting from line 235
where I retrieve EPSG code to save it as a value of srsName - GML
attribute.


I hope it helps or may be anyone knows a better way?

Cheers
-- 
Mateusz Loskot
http://mateusz.loskot.net