AW: AW: [mapguide-users] MrSID problem: RasterIO skipped for oddwindowor buffer size

[Frank Warmerdam]

G.E.O.-Consulting / Hans Mörschell wrote:
> Hallo Frank,
> 
> yes, my MapGuide mapextent is based on the world file because of other
> datasets in that coordinate system.
> 
> If GDAL uses the internal georeferencing is there a way to control this
> behaviour ????

Hans,

There is currently no mechanism to make GDAL use worldfiles in preference
to internal georeferencing in a .sid file within the MrSID driver.  If
you construct an XML config file to for the datasource you can override
the origin and pixel size information by editing the XML.  But I'm not
sure how end users are expected to construct such XML config files currently.

You can also construct a "GDAL virtual xml file" which wraps another dataset,
and can be used to alter metadata, georeferencing, etc.

With FWTools you might do something like the following:

   gdal_translate -of VRT your_big.sid your_big.vrt

edit your_big.vrt and change the origin in the <GeoTransform> element.

Then point your MapGuide/FDO datasource at your_big.vrt instead of at
your_big.sid.

If you are operating on whole directories, you will need to keep the .vrt
files in a seperate directory.  Make sure you create the .vrt's from the
start in this new directory so that the .xml file will have proper relative
paths to the .sid files.

Best regards,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org