USGS DEM Read Problems

[warmerdam]

Frank,

I forced the usgsdemdataset.cpp to set fVRes = 1.0 and ran gdal_translate
to convert my 10 meter USGS DEM to geotiff.   I also made a geotiff before
the forcing to 1.0.
Then I load the original DEM, and both GDAL produced geotiffs into
Geomatica FreeView V8.2.  I'm sure you're familiar with this excellent tool!

I can get a really nice pixel value inspection of all three layers at the same
time.  Sadly, neither of the GDAL produced files are correct.  I'm fairly
certain the native DEM is being loaded correctly by FreeView because I
have taken a few point samples from our lower res dem of the area and it
matches within a few tens of meters.
I've attached the DEM so you can take a look.  I have been examining the
usgsdem loader quite a bit, and can't make out what is going on wrong.  I've
even been pouring over the file format spec, and nothing jumps out at me as
being wrong.
Also, I have used Erdas Imagine to convert the DEM file to other file formats
and it appears to get the correct values.

Maybe you can take a look if you get a chance?

Thanks,

Mark Aubin 

---

File is 39109h1.dem.gz  ... kind of big to attach.

[warmerdam]

Marked to correct before the 1.2.0 GDAL release. 

[warmerdam]

Mark,

It would appear there is also a per-profile elevation offset value that
needs to be applied after using the fVRes value.  With this in place I seem 
to get values compatible with PCI FreeView 8.0. 

Changes committed.