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Hi,
Yes, Christoph, there is a 16-bit PGM format. Due to image browser
problems,
I didn't discover this until I had done some research on the internet.
I had forgotten that I had downloaded PBMPlus a couple of years ago.
The package (now NetPBM) was written by the developers of the format).
After several hours of research, locating new accessory utilities to
handle the 10 meter file size (9+Mb), I've converted a 10 meter DEM to
Povray's Targa format.
While I've found the utilities neccessary (and free)to do the job,
I've given some thought to the conversion of PGM to Pov-Targa using
PPM (Portable Pixel Map)from the same developers.
Eventually, I'll run into scaling problems when I exceed the 65535 limit
on the Targa/PGM formats. The 10 meter DEM elevations, in addition to
adding horizontal (x, y) detail, they also add vertical (z) detail which
shows
up in the form of the addition of a decimal digit to the elevation data
format
where in the 30 meter, all data are integers.
As an example, The test sample had elevations from 480-1100 meters.
To adapt the data to 16/24-bit PGM format, I had to multiply the data by 10
to remove the decimal point and return the format to integer. Either this
method or the removal of the decimal portion ( which would introduce an
error) had to be done. If not, then I would have had to write a program to
round the decimal portion off, which would also introduce an error factor.
Given the Povray Targa format leaves the blue band open, I wonder if they
might consider using it to expand the graphic resolution to 32-bits.
Anyway, thanks to everyone for their responses, especially Mark for
reminding me of the Portable Bitmap set of formats.
Thanks again,
Jim
A list of the utilities I ended up using:
3DEM (DEM manipulation program)
Wilbur (DEM manipulation program)
PFE (Programmer's File Editor) - large text file editing
HL-LAB (John Beale's HeightField Lab): PGM - TGA conversion
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