[Geotiff] Orthophoto in Fathoms?

Chris 'Xenon' Hanson xenon at 3dnature.com
Fri Mar 9 12:55:20 EST 2007


   While doing support for one of my users yesterday, I encountered a very strange 
georegistration problem. The coordinates in the GeoTIFF file seemed reasonable for her 
projection (UTM NAD83), but my software (Visual Nature Studio) was getting them all wrong. 
It turns out that my units conversion code was multiplying them all out by some odd 
factor. Digging further (on the user's computer, via VNC) I discovered via Listgeo that 
the orthophoto appeared to be claiming its projection was using units of FATHOMS.

   Huh? That doesn't even make sense. Anyone ever seen anything like that?

   I'm pestering the user to get the listgeo dump text sent to me so I can share it here, 
but I don't have it yet.

   The file claimed to be written by IMAGINE (and the user confirmed this) cropped from a 
UTM/meters orthophoto that was originally a MrSID. Other software (ArcGIS) seemed to be 
utilizing the Fathom-based file just fine and registering it properly. I can only assume 
they were ignoring the weird Fathom tag. I can't imagine a legitimate use for 
units=Fathom, so I'm considering hacking my code to sanity-check that and set it to meters 
to avoid stupidity.

   Any comments?

-- 
      Chris 'Xenon' Hanson | Xenon @ 3D Nature | http://www.3DNature.com/
                    3D Terrain: http://3d-terrain.com/


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