CE 397 GIS in Water Resources Spring 1995

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:

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.
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.
- If you see the actual file apear in your browser window (i.e. a bunch of ASCII characters) your browser was probably able to unzip the file automatically. This happens when using the Netscape on the DEC Alpha workstations in the Learning Resources Center (LRC). If this happens you still have to save the file to your local workspace by choosing the save as option. Give the file a name like Austin_w.dem. Then you can go to step 3.
- If your browser prompts you for a location to save the file to, your browser probably does not know how to handle the file. Enter the location where you want the file saved to. You still have to unzip the file. Go to the Terminal window in the directory where the file is located and type:
  $ gunzip filename (e.g. Austin_w.dem.gz)
  This will yield a file called austin_w.dem.
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.
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.
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.

Exercise 2: Delineation of Watersheds and Streams

CE 397 GIS in Water Resources University of Texas at Austin

CE 397 GIS in Water Resources
University of Texas at Austin