Even, I feel that the RPC coefficients have well establish meanings from the NITF spec, and file formats like _rpc.txt. I assume they are center-of-pixel oriented. I would *not* want the RPC metadata we keep (ie https://trac.osgeo.org/gdal/wiki/rfc22_rpc) to have a different meaning for the pixel/line locations. So I would suggest we should not need to transform the RPC coefficients when they are imported - instead it is the evaluator which needs to adapt between the RPC pixel/line model and the usual GDAL interpretation.
I'll note this opinion in the ticket as well. This is going to be moderately distruptive. :-( Pablo - thank you for bringing this to light! Best regards, Frank On Fri, Jun 19, 2015 at 7:35 AM, Even Rouault <even.roua...@spatialys.com> wrote: > Le vendredi 19 juin 2015 15:47:54, Pablo d'Angelo a écrit : >> Dear GDAL Developers, >> >> i have recently compared the results of our internal RPC based >> orthorectification software and have found several difference, which I >> think are due to various "corner" vs "center" of pixel issues in the RPC >> transform code. This lead to significant shifts when using lower >> resolution DEMs, such as SRTM, particularly in hilly and mountainous >> regions. >> >> I have prepared an analysis and patches to fix these issues at: >> https://trac.osgeo.org/gdal/ticket/5993 > > Hi Pablo, > > I had seen your well documented ticket and wanted to give feedback. Thanks for > the reminder. > To my opinion, adjustments between "vendor"/formats conventions and the GDAL > convention (0,0=upper-left corner of upper-lef pixel) should be done during > the reading of the RPC parameters from their source (similarly to what is done > when reading a geotransform with pixel-is-center convention), so as to make > the > https://trac.osgeo.org/gdal/attachment/ticket/5993/fix_RPCTransformPoint.patch > patch unnecessary. > Apart .rpb and .rpc_txt, we can also read RPC from GeoTIFF, NITF, ENVI, > Oracle, PCIDSK... so I'm wondering what our situation is related to them. > Of course this also leaves the embarassing question of which convention to > adopt when writing RPC values in .rpb or _rpc.txt files... Probably DG > convention for .rpb ? > > fix_rpc_dem_interpolation.patch looks good to me. > > Even > > -- > Spatialys - Geospatial professional services > http://www.spatialys.com > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, warmer...@pobox.com light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Software Developer _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev