Morris Trimmer TRIMMER at fs.sciences.WLU.EDU
Fri Jul 22 10:46:58 EDT 1994

Jeri, Matt and others,
 I recently had problems and questions about importing 1deg DEMs 
(from edcftp.cr.usgs.gov/pub/data/DEM/250) and received the helpful 
message below.  Also very helpful for learning about DEMs and what 
the numbers in the header mean I suggest you look at the info via 
Mosaic http://edcwww.cr.usgs.gov/glis/hyper/guide/1_dgr_DEM
( if you dont have access to Mosaic I can send you an eddited copy).  
Also, get a copy of USGS booklet "Digital Elevation Models, Data 
Users Guide"
---begin included message---
The following is a set of general instructions and a specific example 
of the commands used to import 1 degree by 1 degress dem data:


1)   dd if=diskfilename ibs=10240 | \
          m.dmaUSGSread top=1 bottom=400 left=1 right=500 \
              output=dem logfile=log

      Of course you need to substitute the right parmaters to describe 
the portion of the 1 degree by 1 degree area which you wish to 
extract; in this example the first 500 columns of the first 400 rows of 
data. These two paramater remain the same for steps 2 and 3. The 
blocking paramater (ibs) should NOT be changed, regardless of area
quad, etc.

2)      m.rot90  input=dem  output=dem.r90
          rows=400  cols=500  bpc=2

3)    Create a region (in UTM coordinates) with g.region, then

     r.in.ll input=dem.r90 output=dem.utm
             dimension=500,400 bpc=2 res=3,3
             corner=sw,37:13N,103:45W spheroid=wgs72

     in the last command you have to give lat-long for a corner of your 
dem using the wgs72 spheroid.  The r.in.ll command should create all 
the necessary support files for you.  But if you run into problems, just 
run r.support.   

[Note: Unlike the above instructions, in the following session I loaded 
the entire 1 degree by 1 degree area, i.e., 1201 rows by 1201 cols of 

Mapset <dem> in Location <whatever>
GRASS 4.0.2 > dd if=tulsa_w.dem ibs=10240 | m.dmaUSGSread top=1 
bottom=1201 left=1 right=1201 output=tulsa_w.out logfile=tulsa_w.log
The requested window is:
rows: 1-1201, cols 1-1201
863+1 records in
17261+1 records out

Mapset <dem> in Location <whatever>
GRASS 4.0.2 > m.rot90 input=tulsa_w.out output=tulsa_w.rot90 
rows=1201 cols=1201 bpc=2

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