All:
I've consolidated many gtopo30 DEM files covering the North American
Continent and have been doing a quality check on the info, mostly over
California. I find California has a new geographic feature I was not aware
of. It is a moat surrounding the foothills of the Central Valley ranging
from a few meters to more than a hundred meters below sea-level. (Was this a
big quality control hole in the otherwise excellent gtopo30 project, or did
a hacker place modified DEM files in place of the originals. DEM
documentation indicates my lowest point in the combined dataset should be
Death Valley, Ca. at -79 meters?). Last I checked the peripheral canal is
not yet built do to public opinion.
I am curious as to whether anyone else has experienced and/or resolved this
issue, and what steps were taken to make the corrections. I need a solution
soon as I think my small humble abode is going under in its current
location, at least according to the gtopo30 DEM, and I'd like to bring it
back up to the correct elevation. 
If there are other errors around the N. American Continent in regards to
the gtopo30 dataset please let me know. I am also looking for other
potential 'free' DEM data sources with the same or better resolution as
gtopo30.
If you can help with either issue please drop a line to kcross@ecis.com.
TIA
KC
On Sun, Feb 11, 2001 at 05:05:21PM -0800, ECIS Mail wrote:
All:
I've consolidated many gtopo30 DEM files covering the North American
Continent and have been doing a quality check on the info, mostly over
California. I find California has a new geographic feature I was not aware
of. It is a moat surrounding the foothills of the Central Valley ranging
from a few meters to more than a hundred meters below sea-level. (Was this a
big quality control hole in the otherwise excellent gtopo30 project, or did
a hacker place modified DEM files in place of the originals. DEM
documentation indicates my lowest point in the combined dataset should be
Death Valley, Ca. at -79 meters?). Last I checked the peripheral canal is
not yet built do to public opinion.
I am curious as to whether anyone else has experienced and/or resolved this
issue, and what steps were taken to make the corrections. I need a solution
soon as I think my small humble abode is going under in its current
location, at least according to the gtopo30 DEM, and I'd like to bring it
back up to the correct elevation.
If there are other errors around the N. American Continent in regards to
the gtopo30 dataset please let me know. I am also looking for other
potential 'free' DEM data sources with the same or better resolution as
gtopo30.
If you can help with either issue please drop a line to kcross@ecis.com.
Hi,
you may check the GLOBE DEM 30 data, they could be of better quality:
http://www.geog.uni-hannover.de/grass/faq/globedem.html
Regards
Markus Neteler