EXTRACTION of DEMs into lat-long locations

[Olga Waupotitsch]

Here are more complete directions to import DMA data
I suspect you geographic region and resoulutions weren't set
up correctly:

ftp site: resdgs1.er.usgs.gov


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 parms for your area.  (I left
       the blocking parm as above.)

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
      use m.ll2u to convert nothings and eastings of them map
      to utm. (first divide them by 3600, adjust ew_res and ns_res
      so that there are 1200 rows and 1200 cols.

     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 command above 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.