extracting DEM data

GRASS GRASS user
1

hi,

i have recently installed Grass4.1 on a SunSparc server and have
started setting up some data layers for los angeles. i have imported
Tiger files with no problem. But now i can't seem to import DEM files
with any success.

1) is there a tutorial for m.dem.extract or other ways to import DEM files?

2) otherwise, here is what i am trying:
  a) obtained DEM files from usgs ftp site.
  b) start grass set to my LA database
  c) use g.region to set region to something slightly larger than
     the header info from the DEM indicates
    set res to 00:00:03
  b) using m.dem.extract to extract data
     setting start and end file number = 1
  c) data extraction completes successfully with 1201 rowsxcols
  d) d.erase; d.rast shows only single color for entire display

am i missing some step? i even tried changing the color table with r.colors,
and running r.support explicitly, but with no change. i can display my
Tiger data maps without any problems. any help would be appreciated.

thanks very much,

gurcharan s khanna
university computing services/
dept. of geography
univ. of southern california

this is the txt file accompanying the DEM file:

Raw Digital Elevation Model Data Holdings, DSDL - Reston
     
    *File Name: los_angeles_w DEM Level: 1
    *Source Date: XX/19XX Process:
    *Inspected or revised: NO Date: NONE
    *Mapping Center:
    *Number of rows: 1201 Number of columns: 1201
    *Minimum Z value: 0.0 Maximum Z value: 2682.0
    *Resolution X: 3.0 Y: 3.0 Z: 1.0
    *Coordinate System: GEOGRAPHIC Units: ARC-SECONDS
    *Vertical datum: NGVD29 Horizontal datum: WGS72
    *
    *Minimum_latitude: 34
    *Minimum_longitude: -120
    *Maximum_latitude: 35
    *Maximum_longitude: -119

2

On Tue, 23 Nov 1993, Gurcharan Khanna wrote:

hi,

i have recently installed Grass4.1 on a SunSparc server and have
started setting up some data layers for los angeles. i have imported
Tiger files with no problem. But now i can't seem to import DEM files
with any success.

1) is there a tutorial for m.dem.extract or other ways to import DEM files?

2) otherwise, here is what i am trying:
  a) obtained DEM files from usgs ftp site.
  b) start grass set to my LA database
  c) use g.region to set region to something slightly larger than
     the header info from the DEM indicates
    set res to 00:00:03
  b) using m.dem.extract to extract data
     setting start and end file number = 1
  c) data extraction completes successfully with 1201 rowsxcols
  d) d.erase; d.rast shows only single color for entire display

am i missing some step? i even tried changing the color table with r.colors,
and running r.support explicitly, but with no change. i can display my
Tiger data maps without any problems. any help would be appreciated.

Not that it is much help, but I am having the same problem. It is strange,
the old version of the command in 4.0 worked fine. The manual said that they
enhanced it, and that it was going to be pickier about headers. It must be
very picky, because I imported 61 dem's and only 12 came in OK.

If you find a fix, could you summarize to the list or mail me a summary
directly?

Thank You,
-Craig

--------------------------------------------
Craig A. Miller
Pacific Northwest Geographics
Voice: (509) 662 4479
E-mail: cmiller@pnwg.wa.com