Contents
Cal Poly Pomona

A map

 

U.S.G.S Topographic Maps

California (DRG) GEOTIFF Images

 

 

Until recently, U.S.G.S. DRG files were  freely available on the Internet.  These files are the digital equivalents of paper U.S.G.S. 7.5' topographic maps.  However, private companies are now charging for the digital map files that were created by the U.S.G.S.  Fortunately, the state of California has an agreement with the Federal government that makes the files available free of charge (California only) through a server located at the Cal-Atlas Geospatial Clearinghouese.  For reasons that are not clear the front-end that allows you to readily locate the map you need was never completed.  The maps simply exist in folders arranged by latitude and longitude with no index.  The Geological Sciences Department at Cal Poly is attempting to create an index for these maps (see instructions below).  At present we have created an index for eleven counties in southern/central California.

To obtain the map you need follow these steps

  1. If you don't know the quadrangle maps you need click on this link to MapMart.  Make sure you are in the U.S.G.S Digital Raster Graphics section. Choose 1:24,000 is selected and click on the Begin Search button to the right.  You will be presented with a zoomable map of the United States.  Click on California and proceed to Zoom In until you find the names of the quadrangles you want.  If those quads are in one of the eleven counties listed above, proceed to step two.  If not, you are on your own for now.

  2. Click on this link to the Cal Poly Topomap Database.  Using your browsers Find command, enter the name of the quad(s) you are seeking.  You will see a seven character alphanumeric number next to the quad name.  Write this number down and click the back button on your browser.  You are now ready to go to step three.

  3. Click on this link to go to the Geospatial Clearinghouse.  Maps are arranged by a seven digit code realted to latitude and longitude. Scroll down the list until you find the map you are seeking; Click on the pertinent file folder and you be taken to another page that offers various color image, DOQ and DRG downloads for that quad. Use a Save Target As on the file (.tif) to download the quadrangle.