Exercise 2: Delineation of Watersheds and Streams

CE 397 GIS in Water Resources
University of Texas at Austin

To download and use data over the internet do the following:
  1. Download the data from the U.S. Geological Survey. If you want to work with the the West portion of the Austin mapsheet, download the compressed AUSTIN-W DEM.
  2. The file is compressed with a utility called gzip which creates files with a .gz extension. Depending on how your web browser is configured you might have to uncompress the file yourself.
  3. Rearrange the block size correctly for Arc/Info processing. Type:

    $ dd if=austin_w.dem of=austin_w2.dem cbs=1024 conv=unblock

    This produces a correctly blocked file called austin_w2.dem.
  4. Convert the file to Arc/Info format. Start Arc and type:

    Arc: demlattice austin_w2.dem ausdem usgs

    This produces an Arc/Info grid called ausdem which is the raw DEM data in geographic coordinates.
  5. Note that the file is not in export format which means it does not have to be imported with the Arc/Info import command as described in the intstructions.