[gdal-dev] Altering the GeoTransform matrix with World files and VRT files

[Craig Leat]

Hi,

I have a collection of MrSid images with embedded georeferencing
information and accompanying world files. The world files have correct
geotransform values, but the information embedded in the sid files is
incorrect. My installation of gdal 1.7 gives precedence to the
embedded georeferencing over the world file. Based on this mail [1], I
understand that this order of precedence was a gdal design decision
and I need to use a vrt file to alter the geotransform. Since I have
many files and I don't expect that the government supplier will
correct the data for me I have started writing a script to generate
the vrt files and then alter the geotransform in the vrt based on
values found in the world file.

Before I proceed much further I wish to pose two questions:
1. Is there a gdal environment variable I may have missed that can be
used to give precedence to the world file?
2. Is there any freely available software that will modify the
metadata tags in a sid file?

PS I would rather not translate from sid to tif.

Much thanks,

Craig

[1] http://n2.nabble.com/Georeferencing-Mrsid-raster-file-with-a-world-file-td1994277.html#a1994280