[Gdal-dev] netCDF driver GeoTransform bug

[Julien Demaria]

Hi,

I have found a bug in the computing of the GeoTransform in the function 
netCDFDataset::SetProjection of the netcdfdataset.cpp file (last version): the 
resolution was wrong and the origin was the center and not the upper-left corner:

	poDS->adfGeoTransform[0] = pdfXCoord[0];
	poDS->adfGeoTransform[3] = pdfYCoord[0];
	poDS->adfGeoTransform[2] = 0;
  	poDS->adfGeoTransform[4] = 0;
  	poDS->adfGeoTransform[1] = (( pdfXCoord[xdim-1] -
  	                              pdfXCoord[0] ) /
  	                            poDS->nRasterXSize);
  	
  	poDS->adfGeoTransform[5] = (( pdfYCoord[ydim-1] -
  	                              pdfYCoord[0] ) /
  	                            poDS->nRasterYSize);

should be corrected with:

	poDS->adfGeoTransform[0] = pdfXCoord[0];
	poDS->adfGeoTransform[3] = pdfYCoord[0];
	poDS->adfGeoTransform[2] = 0;
  	poDS->adfGeoTransform[4] = 0;
  	poDS->adfGeoTransform[1] = (( pdfXCoord[xdim-1] -
  	                              pdfXCoord[0] ) /
  	                            ( poDS->nRasterXSize - 1 ));
  	
  	poDS->adfGeoTransform[5] = (( pdfYCoord[ydim-1] -
  	                              pdfYCoord[0] ) /
  	                            ( poDS->nRasterYSize - 1 ));
	poDS->adfGeoTransform[0] = pdfXCoord[0]
	      - (poDS->adfGeoTransform[1] / 2);
	poDS->adfGeoTransform[3] = pdfYCoord[0]
	      - (poDS->adfGeoTransform[5] / 2);

Maybe there is also the same problem just after this code when trying to 
retrieve the geolocation from the attributes like "Northernmost_Northing", 
depending if these attributes define border or center pixel:
	adfGeoTransform[0] = dfWE;
	adfGeoTransform[1] = (dfEE - dfWE) / poDS->GetRasterXSize();
	adfGeoTransform[2] = 0.0;
	adfGeoTransform[3] = dfNN;
	adfGeoTransform[4] = 0.0;
	adfGeoTransform[5] = (dfSN - dfNN) / poDS->GetRasterYSize();


Regards,

Julien