• Each zipped file contains:

    • four (4) image files (.sid)--one for each quarter quad in the selected 7.5' quadrangle. The quarter quad is designated in the filename by a suffix of a, b, c, or d indicating northeast, northwest, southwest, and southeast, respectively
    • associated world header files (.sdw) in NAD83 format
    • header files for both NAD83 (.n83) and NAD27 (.n27) format
    • a general header information file (.hd), which contains the source image date. See a map of the dates the photos that make up the DOQs were taken

  • The files for download have been compressed using MrSID compression software.  ESRI's ArcView software versions 3.1 and later have the capability to display MrSID files when added as image themes. 
  • Download the ExpressView Browser Plugin  by LizardTech to view these images with your internet browser. 


   Click on an area of the map to zoom in.


Click to zoom in to quads