Digital Orthophoto Quarter Quadrangles

Data Description | Data Location

Data Description

• Digital orthophotos of certain areas are available for quarter quad portions of the 7.5 minute USGS quadrangles. Digital orthophotos are digital images derived from scanned aerial photographs differentially rectified so that image displacements caused by camera tilt and terrain relief are removed. The current production of DOQQ's is based on 1:40,000 scale black and white photography scanned with a 25 micron aperture resulting in a ground resolution of one meter. Each quarter quad file is approximately 55 megabytes.

• The distribution format of the digital orthophoto file contains four ASCII header records, followed by a series of 8-bit, binary image records. The digital orthophoto is cast on the Universal Transverse Mercator (UTM) projection on either the North American Datum of 1927 (NAD 27) or North American Datum of 1983 (NAD 83).

For more information on DOQQ's, see the USGS DOQ web site.

Data Location

UC Santa Barbara is now serving all of the available USGS DOQQs for California to the public at no cost.

• To access these data, go to http://webclient.alexandria.ucsb.edu/ and in the left frame, for #2, "Collection to Search", select "…DOQQ B&W Calif"
  
• Then search by geographic area or quad name. Once your quad of interest has appeared in the window on the right, click on Access/Download.
• Scroll down to #2 > Access/Distribution > Download files > Download DOQQ Image > and right click on the link to your quarter quad.
  
• Select Save Target/Link As, and store the file on your hard drive.
• After you download the file (ex: O3411935.NWS), you need to convert it to GeoTiff format to open the image in GIS software.
• The conversion can be done with this program: doq2geotiff.exe (Save it to disk)
  
• Open a DOS window (command prompt).
  
  • Run the doq2geotiff.exe by pointing to the .exe file, listing the input filename, and naming an output filename.
• For example:

C:\doq2geotiff.exe O3411935.NWS O3411935NWS.tif

(If you store the image in a stacked folder, always give the full path name: C:\DOQQs\CA\tamarack\doq2geotiff.exe C:\DOQQs\CA\tamarack\O3411935.NWS C:\DOQQs\CA\tamarack\O3411935NWS.tif)

You can then add the GeoTiff image to ArcView or ArcGIS.