However, if you're not interested in downloading these (and feeling rather adventurous) you can download other DEMs of
In this case, you will need to complete all the steps below. Other states in the UNIX-compressed form .tar.gz format are located here.
The sample procedure for a different California DEM (one that wasn't downloaded from above) is outlined below.
For a printer-friendly copy of this, click here.
California USGS DEMs at CSU Northridge through Truflite:
- You'll see a large map of California. Wait for it to fully load.
- When complete, scroll down, and click on an area in which you would like to zoom in.
- The next map will further show 7.5' boxes outlined in green of individual DEMs. Again, wait for the map to fully load.
- Click on the area you want to download.
- Select Save As...
- Navigate to your directory.
- Click Save. Note where you saved the file. It may take a while to download.
Or it may be in the blink of an eye, depending on the connection. Watch carefully.
- You will then need to go into your account in UNIX under X-Win32 (Start, Programs, XWin-32, XWin-32):
- Go to the directory in which you downloaded the file.
- ...and gunzip the file you just downloaded. At the prompt (%) type:
Not much will happen if it gunzipped it successfully. You should just get a prompt on the next line.
- Then, rename the file with a .dem extension so that ArcView can read it. Type:
mv filename_dem filename.dem
Loading the DEM
Next, fire up ArcView.
- Open a new View window.
- Activate the Project window (will probably have "Untitled" in its menu bar) by clicking in/on it.
- Go to File...Extensions....
- Check on the Spatial Analyst module, and then click OK.
- Click on the View window to select it.
- Go to File --> Import Data Source...
- Select USGS DEM in the drop-down menu; click OK.
- Go to your directory and select the DEM you prepared above. It should have a .dem extension.
- In the Output Grid dialog box, make sure you are in YOUR directory and not C:\temp.
This will make your life much easier later. In the Grid Name field, name the
output grid whatever the name of the DEM was called (with no extension). For instance, if the DEM you downloaded
and prepared was called frink.dem, you would simply name it
Frink in the dialog box.
- Watch it work on importing and calculating the DEM lattice. This could take a while.
- At this point, one of two things will happen (if the above completed successfully):
- A new box will pop up asking whether or not you would like to add this new grid to the View, or;
- You have to add it in yourself. If this occurs, add a new theme (Theme...Add Theme...)
to get it in the View window. Instead of Feature Data Source,
select Grid Data Source,
and find your DEM in your directory and click OK.
- Adding a Grid Data Source can sometimes take a
few minutes, depending on size, and speed of processor.
- Eventually, the legend to the left of the View window will show a color scale and a range of values.
Click on the little gray box to the upper left of this color scale, and the DEM is drawn.
Manipulating the DEM