ITCHy GRASS problem with DEM tapework
sm646601 at longs.lance.colostate.edu
Sat Mar 21 13:36:44 EST 1992
I am walking through some tall GRASS and need to help me with an ITCH
(Interesting Technical CHallenge) I have developed involving 7.5 min
1:24,000 scale DEM extraction from tape.
The tape I am working with contains five DEM files,
USGS, NMD, Data Base Office, USGS tape PNA821
1:24,000 scale DEM 7 meter data
9-track density=6250 BPU-Label=None Rec Len=1024, Blocksize=8192
I originally examined the tape with
m.examine.tape input=/dev/rst17 blocksize=8192 > dem_list
where /dev/rst17 is a SCSI driver for
6250 density 9-track used locally.
CERL supports rmt0 (magnetic tape) drivers, however the drive I have
access to with GRASS4.0 uses a SCSI interface /dev/rst17
The information matched the accompanying printout for each of the files.
I proceeded to examine information using the DEM examine tool:
m.dem.examine input=/dev/rst17 blocksize=8192
I experienced mixed success, and with the system administrators help
retreived the indivdual files using a UNIX dd:
dd if=/dev/nrst17 of=<rx> bs=8192
where <rx> is a sequenctial file counter r1, r2, ..., rn
I examine the files and found
rx Description (Taken from 1st line of file)
r1 GUSTINE, CA CTOG DLG2DEM
r2 STEVINSON, CA CTOG DLG2DEM
r3 INGOMAR, CA CTOG DLG2DEM
r4 SAN LUIS RANCH,CA CTOG DLG2DEM
r5 LOS BANOS,CA CTOG DLG2DEM
Information looks ok, and attempted to uses GRASS4.0 tools to
extract from file. For reference, I am working in a subdirectory
in the PERMANENT mapset.
The g.region command was used to set a bounding area beyond beyond the
UTM coordinates for the entire five quad region. I work through the
m.de.extract input=<rx> output=<quad_name>.dem blocksize=8192
This produces a raster file with zero elevation. Use of r.support has
no categories and I see a perfectly flat map when rendered with d.rast
or d.display. Where am I making an error.
Several reblocking tricks were suggested by local expereinced GRASS3.x
and 4.0 users without success. I have captured output to files that
could be exchanged on a personal basis if needed. I would like to
resolve this problem, and perhaps post a sequence for other SCSI driver
users with my tape scenario.
Can anyone help me scratch my ITCH?
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