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FAQ (Frequently Asked Questions)

1. How do I request digital map files that are not posted on your site?
   
   We generally try to procure digital map files to support University of Nevada research.  Please contact us to request files for UNR research.  We will refer non-UNR requests to appropriate government and commercial providers.
    
2. Can you supply DEMs that are not posted on the Keck site?
   
   Yes and No.  We do serve 1 degree by 1 degree NEDs files for the entire state.  NEDs are built from the same digital elevation data used in DEMs.  Our recommendation is that you either contact USGS to purchase DEMs you need, or clip coverages from NEDs files available on this site.
    
3. How do I "clip" coverages from NEDs files?
   
   To clip a NED grid file, download the "GridClip " Avenue script from the ESRI website. The script is authored by Stefan Giese and dated 3/19/01. Load the script into the "EXT32" folder in your ESRI directory and open the Spatial Analyst and ClipGrid extensions when opening ArcView. The "ClipGrid" icon is an orange square inside a point grid. Simply click on the icon and use the pointer to make the rectangular clipped grid your interested in. The clipped grid can be renamed and used as any other grid file.
    
4. Where can I learn more about the various digital map files you serve?
   
   The main webpages for the DEM’s, NED’s and DRG’s have a section labeled "About". There is a brief explanation of the digital map and a link the USGS webpage that goes into further detail about the type of map you’ve chosen. Information on other types of maps can be found at the main USGS website. Information on Landsat can be found at the main NASA Landsat website. Information on SPOT satellite imagery can be found at the main SPOT website.
    
5. More about Landsat files available on this site.
   
   The Geospatial Data Clearinghouse provides access to Landsat TM Images for Landsat 1984/88, Landsat 1992/93 and Landsat 7.  Landsat 1984/88 TM false color composite images are available in JPEG format.  Raw band data can also be accessed by clicking on the appropriate path/row.   If you know the exact path and row, go directly to the list of available Landsat 1984/88 TM, Landsat 1992/93 TM, and Landsat 7 ETM+ data.  NASA provides a thorough online Remote Sensing Tutorial 
     
6. How do I view a Landsat composite image?
   
   Full scene images are viewable from each path/row webpage. The image can be downloaded and saved to a file by clicking on the "Download JPG Image’ link or can simply be viewed by clicking on the thumbnail image icon. Each TM image (JPEG) has been geocoded and registered in UTM coordinates. Please note that all images are accompanied by a world file (.jgw) which provides geocoding information. The world files are needed in order to view the images in ArcView (UTM projection). When downloading the image the world file will automatically be downloaded. Each world file shares the same file name as the image that it describes but with the .jgw file extension. JPEG images range from 133 to 229 KB in size. These images are not high resolution and should be used for regional presentations.
    
7. How do I view geologic maps?
   
   Geologic maps are compressed using ECW compression software.  A free plug-in is available from ER Mapper which will allow you to uncompress the geologic map files.  Follow the directions below:
   
   1) Download the ECW Arcview plug-in.
   2) Double-click on "Downloads" on the upper bar on the ER Mapper web page.
   3) Scroll down to ECW Downloads and click on "ArcView ECW and ER Mapper Plug-in v.2.3".
   4) Scroll down to "Download your copy now (2.895 kb)" and click on the word "download".
   5) You must register by filling in your personal data when prompted.
   6) After you've registered, click on "software" on the "Download the software (2.895 kb)" line and install the software using the ER Mapper instructions.
   7) After the software has been installed, open ArcView, go to Extensions under "file" and load the ECW extension.
   8) After downloading the geologic maps files you've chosen to view, unzip the files using pkzip or Winzip.
   9) Open the geologic map as a view and specify "Image Data Source" under "Data Source Types".
   10) Chose USGS_"map number"_UTM for a georeferenced map in UTM coordinates or USGS_"map number"_RAW for the map with all the collar information such as explanation, title, scale bars, etc.
    
8. More about SPOT files available on this site.
   
   These images are distributed by the U.S. Geological Survey (USGS) with data provided by the National Imagery and Mapping Agency (NIMA).  SPOT files are 10 Meter Resolution Digital Orthorectified Imagery (DOI-10) derived from data obtained from the SPOT Image Corporation under an unrestricted license.  SPOT data is described in detail on the USGS web site.

The University of Nevada, Reno, DataWorks is developing this site to provide students, researchers, and the general public access to public domain spatial data in easy-to-use formats.