Overriding GeoTIFF projection with world file

[Rahkonen Jukka]

Frank Warmerdam wrote:
 
> Rahkonen Jukka wrote:
>> Hi,
>>  
>> I must use two different projections (epsg:2393 and 3067) which both 
>> have a common centre meridian 27°E.  One is transverse Mercator with 
>> scale factor 1, another UTM with scale factor 0.996.  Now I can use the 
>> same images, without any physical or on-the-fly reprojection simply by 
>> creating two sets of world files with adjusted origos and pixel 
>> sizes. Actually in my case this leads also to better accuracy because 
>> another system has some local distortions which I can compensate by 
>> sliding the origo to correct place with world file.
>> But I have a problem: vast majority of my images are in GeoTIFF format 
>> having internally defined coordinate system epsg:3067.  I wonder if 
>> there is some trick to override this projection by world files.  
>> Something like a hidden switch TRUST_WORLDFILE=YES which I could use in 
>> the mapfile.  Does such a switch exist?

>Jukka,

> I'm afraid there is no such option.

> Alternate approaches include:
> 1) reprocess the tiff so it has no internal geo information.  For example,
    with gdal_translate -co PROFILE=BASELINE

Yes, I know that this would work, but I hate this option anyway.  I have 20000 image files and removing geoinformation from them would take at least 3 minutes per image. Even one minute per image would mean 333 hours.  And I would like to keep the internal geoinformation inside the image file because usually it is extremely useful.

> 2) Create a VRT wrapper for the TIFF in which you can modify the geotransform
    and then use that VRT proxy in place of the TIFF.
> 3) well, I'm sure there are other methods.

How about trying to motivate some clever developer to create the option I mentioned... Point 1) might give me possibilities for making an investment.  I fear this feature is not too much of general interest.

-Jukka-