Hi Jukka, > > Sometimes an image can have several and ambiguous metadata for > georeferencing. Mapserver has a method to deal with ambiguous internal > geotiff metadata and world files and user can override the internal > metadata by using PROCESSING "EXTENT_PRIORITY=WORLD" in the mapfile. > http://www.mapserver.org/input/raster.html#special-processing-directives. > I thought it was PROCESSING "EXTENT_PRIORITY=WORLDFILE" but perhaps both > keywords are supported. > > I wonder if GDAL supports this same worldfile override with some secret > config option. At least it is not listed on page > http://trac.osgeo.org/gdal/wiki/ConfigOptions. > > I can also see that GDAL does have a config option GMLJP2OVERRIDE but I > could not easily find what is is doing.
/* -------------------------------------------------------------------- */ /* This is a backdoor to let us embed a literal gmljp2 chunk */ /* supplied by the user as an external file. This is mostly */ /* for preparing test files with exotic contents. */ /* -------------------------------------------------------------------- */ > > And finally when I was playing with a "gdal_edit.py" utility I discovered > that there are at least 4 ways to georeference a JPEG2000 file: > - use worldfile .wld or .j2w > - use internal GeoJP2 (GeoTIFF) georeferencing > - use internal GML georeferencing > - use an external .aux.xlm file > > I noticed that command > python gdal_edit.py -a_srs epsg:3067 metajp2test.jp2 > was creating a file names "metajp2test.jp2.aux" which does contain the > right georeferencing data. > However, if I run gdalinfo it is looking for > the internal GeoJP2 metadata and it reports that my JPEG2000 file is still > using an unknown projection. Was it with the JP2OPENJPEG driver ? JP2KAK and JP2ECW should return what is found in .aux.xml. I also agree with Frank that PAM information should override internal information. In the case of JPEG2000, I think it might be possible, pending some work, to edit the JP2 boxes to rewrite the GeoJP2 and/or GMLJP2 boxes in place. Well, maybe not in all cases if the size of the new boxes is larger than the old boxes. In which case a utility could rewrite a slightly larger file by shifting the compressed imagery off a few bytes, but without modifying it at all. > > This feels a bit messy. Perhaps there is a need to have a GDAL wide config > option for what metadata to search and use for georeferencing. In my case I > would like to set it to use "external GDAL aux.xml". In addition, I think > that this setting should be made safe so that if aux.xml file is not found > then the image is considered to be without georeferencing. Or perhaps the > config option could take a list like "auxiliary_xml,GeoJP2" with all the > acceptable alternatives in priority order. > Even -- Geospatial professional services http://even.rouault.free.fr/services.html _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
