1
references: <01I1S7YNH06A003NE8@VMGW.AGR.CA>
content-type: TEXT/PLAIN; charset=US-ASCII
organization: University of Illinois at Urbana
mime-version: 1.0
reply-to: grassu-list@max.cecer.army.mil
newsgroups: info.grass.user
originator: daemon@ux1.cso.uiuc.edu
On 29 Feb 1996, Greg Travis wrote:
I have purchased DEM data from our provincial dept of surveys
and mapping. The format is not the same as that used in USGS
DEM's and consequently, I cannot use m.dem.extract. If possible,
I would appreciate a terse description of the format the USGS
provides their DEM's in and I can re-format my provincial DEM's
accordingly.
I have the following which I think I snagged from the GRASS WWW site:
-----8<-----
Importing USGS 1:250,000 DEM data
These instructions are specific to 1 minute USGS dems with 3 arc-second
grid spacing of the type available at EROS Data Center. For determining
which data set you need, you can use their Web interface or else if you
want to automate the process, copy this list of coordinate bounds and file
names for use in your script.
Whether you're working in a lat-lon or UTM database, the first two steps
are the same:
dd if=usgs-file ibs=10240 | m.dmaUSGSread top=1 bottom=1201 left=1 \
right=1201 output=usgs-file.dat logfile=usgs-file.log
m.rot90 input=usgs-file.dat output=usgs-file.dem rows=1201 cols=1201 bpc=2
Then for importing into UTM:
r.in.ll input=usgs-file.dem output=dem.utm dimension=1201,1201 bpc=2\
res=3,3 corner=sw,34N,119W spheroid=wgs72
In the command above you have to give lat-long for a corner of your
dem using the wgs72 spheroid.
Or else for importing into LAT-LON:
Move or copy the output file from m.rot90 to $LOCATION/cell. Look at
the usgs-file.log file and get information to create the
header file (either manually or else using r.support). Or here's a C
program to do this automatically for most US data. You also
need to run r.support to update the range and color table.
To display the new raster, use:
g.region rast=usgs-file.dem
d.erase
d.rast usgs-file.dem
Also see: [r.in.ll] [m.dmaUSGSread] [m.rot90] [m.ll2u] [m.u2ll]
Submitted by: brown@gis.uiuc.edu 8 Dec 1995
-----8<-----
A description of the DEM format can be found
http://edcwww.cr.usgs.gov/glis/hyper/guide/1_dgr_dem
Hope this helps! 
--G
--
Gordon Dewis | WWW Virtual Library Geography Section is now at:
4th year Geography Hons | http://www.icomos.org/WWW_VL_Geography.html
Carleton University | NewForce.ca Sysadmin http://www.newforce.ca