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

[Even Rouault]

Le dimanche 17 juin 2012 18:45:01, Smith, Michael ERDC-RDE-CRREL-NH a écrit :
> I did originally use -dstalpha. I had dropped it when creating the
> geotiffs as I used PHOTOMETRIC=YCBCR as a creation option.
> 
> I'll try with -dstalpha and dropping the YCBCR.

Ah, ok, JPEG compression is indeed incompatible with alpha band. But you could 
however use a mask band, which recent MapServer should handle.

gdalwarp rpc -of vrt -overwrite  -t_srs epsg:3857 -r cubic --config 
GDAL_CACHEMAX 500 -wm 500 $1 $1.vrt -dstalpha

gdal_translate -b 1 -b 2 -b 3 -mask 4  -co "TILED=YES" -co "JPEG_QUALITY=95" -
co "COMPRESS=JPEG" -co "PHOTOMETRIC=YCBCR" $1.vrt $1.tif

gdaladdo --config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW
YCBCR --config INTERLEAVE_OVERVIEW PIXEL $1.tif 2 4 8 16 32

> 
> Is there a known issue with using the vrts inside a tileindex that makes
> it so slow?

RPC reprojection is probably slow, and VRT can add some overhead, especially 
if the tiling scheme it adopts (128x128 blocks) is very different from the 
source raster. Furthermore, if you make a request that is a zoom out, the VRT 
cannot benefit from overviews of the source raster and will make reprojection 
at full scale, before zooming out.