[Geotiff] Linear Units of Projections Parameters

[pw]

I did some experiments using ENVI and Geomatica.

1.) loaded a geotiff that I had previously created
in UTM meter projection. (I don't have any state plane data)

2.) Then converted the image projection to UTM feet in ENVI.
3.) created a GeoTiff using ENVI.
4.) Closed ENVI and reopened it again (clean), reopend the UTM-feet 
GeoTiff. The file came up as UTM-feet. All scales are in feet.

5.) Loaded the UTM-feet GeoTiff into Geomatica. The projection
defaulted to meters with no projection defined. The pixel sizes
where the wrong size, showing values in meters equivalent to the
number of actual feet.

6.) Found that Geomatica has no capability to perform
UTM reprojection in feet.

7.) UTM meters geotiff loads into Geomatica just fine. Projection
is decoded fine.

8.) ArcExplorer wouldn't load GeoTiff as a raster at all. (Crashed)

Hope that's helpful. Let me know if you have
any specific tests you'd like tried.

Peter


Frank Warmerdam wrote:
> pw wrote:
> 
>> Hello,
>>
>> That's a good question. I don't think I've really taken much notice
>> until this question was posed.
>>
>> I use primarily ENVI (RSI) and Geomatica (PCI) and as far as I
>> remember I have never had a GeoTiff image that wasn't in a meter
>> based projection.
> 
> 
> Peter,
> 
> It would be helpful to know specifically if ENVI or Geomatica handle
> the false easting and northing properly.  I wrote the original
> Geomatica GeoTIFF handling, but can't recall the details.  I suspect
> I assumed it was in meters since that is what the internal GCTP
> code at PCI looks for.   Actually, I should be able to check this with
> the PCI free viewer.  Is there still an ENVI free viewer?
> 
> Reports indicate ArcGIS and Imagine assume the false easting and northing
> in GeoTIFF are in meters.  I'm not sure if this might be my fault or not.
> I did some work on that GeoTIFF code too, but I don't *think* I worked on
> the projections details.
> 
> The rest of your email seemed tangential to the issue at hand.
> 
> Best regards,