[gdal-dev] Gdal and Proj GCS/PCS

Guillaume Sueur no-reply at neogeo-online.net
Wed Nov 18 04:54:51 EST 2009

Having just realised that gdal doesn't use proj EPSG file for
reprojection (see my previous post on "Unsupported SRS but available in
epsg file"), I have a few questions to clarify the reprojection
processes both in gdal and mapserver :
- where do the gdal gcs/pcs definitions come from ? Is it a separate
repository or proj source files ? 
- Doesn't ogr2ogr use proj definition files at all ? Does this mean that
an ogr2ogr reprojected file can be different than a mapserver
reprojection result if proj/epsg definition and gdal pcs defs are
slightly different ? 
- If I say "GDAL/OGR uses its own definition files to retrieve proj4
definitions and lets proj4 engine do the reprojection job", am I true ? 

Thanks for these clarifications ! 



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