[gdal-dev] How to use RPC Metadata from NITF Files in a MapServer TileIndex

[Smith, Michael ERDC-RDE-CRREL-NH]

I have a large number of NITF JP2K files. These files have IGEOLO metadata to the second accuracy so reprojecting these images leads to poor results. The images also have rpc metadata and using the -rpc option in gdalwarp reprojects them quite well. These files are source epsg:4326 and need to be reprojected to epsg:3857 for display.

I had orginally thought to just create a vrt for each ntf file with the rpc information but a tileindex of the vrts is dramatically slower to display in MapServer (for a 1:8000 scale area, from ~ 1 sec to over 10 min). It does reproject correctly though. Obviously not practical.

I then thought to reproject the vrts to an actual format (geotiff). The problem is that the black bounds (which should be nodata but are just near black areas) get expanded and aren't handled even when using the nearblack utility on the resulting geotiffs.

The best option (if possible) would seem to use the source nitf files but force gdal to use the rpc information to reproject (without having to go through the vrt process). Perhaps a CPL config option that could be set inside mapserver?

Other suggestions are welcome.

Mike

--
Michael Smith
michael.smith at usace.army.mil
US Army Corps
Remote Sensing GIS/Center
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