[Gdal-dev] Different UTM Zones...

[StefanReisser at t-online.de]

Hi!

I have a huge GeoTiff image and I want to extract that part, that
perfectly matches a specific DEM file.
It's easy, as long as both the image and the DEM use the same projection
and geographic coordinate system. 

However, if the UTM zones are different, or the geographic coordinate
system is different, how can I compute the raster coordinates
of the DEM inside the GeoTiff image?

How can I convert coordinates between different UTM zones and
furthermore, how can I convert between Lat/Long and UTM coordinates?

Thanks for your help!

Stefan