general importing info

[Michael Hanratty]

In message <3.0.1.32.19970701164847.00920a50 at email.psu.edu>  writes:
> I have tried a number of methods to import some USGS data (dem and dlg)
> without success.  

Here's what I've come up with for these two types of data:

Steps for importing USGS DLG files

1. Download from EROS Data Center (keep .gz suffix)
2. Unzip file using gzip -d fname
3. Divide into 80 character lines: fold fname > newfname
4. Import into GRASS: v.import
   Options:
        1
        newfname
        y  UTM projection (sometimes not asked)
        n  Lines, not Areas
        n  Don't do multiple attribute (runs out of memory)
        n  Don't snap


To convert USGS dem files to GRASS format:

1. convert ascii file to binary:
m.dmaUSGSread top=1 bottom=1201 left=1 right=1201 output=binfname
        logfile=logfname < demfname

2. Rotate binary file 90 degrees, creating dem in lat-long format
m.rot90 [-q] input=binfname output=llfname rows=1201 cols=1201
     bpc=2

3. Convert from lat-long to UTM projection and put in GRASS database
 r.in.ll [-s] input=llfname output=rastfname bpc=2
        corner=corner,lat,lon dimension=1201,1201
        res=3,3 spheroid=wgs72
    The latitude and longitude of the sw corner is the first pair of
the 6-digit values in the header of the original dem file.  These six
digit values are arc-seconds.  Divide by 3600 to get degrees. Enter
these values in the corner= input value for r.in.ll.

Hope this helps.


Michael Hanratty                           Phone: (612) 627-4590
St. Anthony Falls Laboratory               Fax: (612) 627-4609
Dept. of Civil Engineering
University of Minnesota
Mississippi River @ 3rd Ave. SE
Minneapolis, MN 55414