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COMPRESSED DIGITAL ORTHOPHOTO QUADRANGLES (COQs) |
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Source: Nebraska Department of Natural Resources Processed by: Data Bank (JH) A Compressed DOQ, also known as COQ, is a Digital Orthophoto Quarter Quadrangle image that has been compressed using JPEG format. Since JPEG is a "lossy" image compression format, a COQ will have slightly less color separation or clarity than that of a DOQ. However, its resolution (1-meter pixel size) remains the same. The COQ requires about 2 MB to 4 MB of storage space per 3.75- minute or quarter quadrangle region. Since a COQ image is compressed, it associated header file should also be retreived separtately. The COQs are also available in World File Format. Follow instructions below: Retrieval of COQs (1999) The Nebraska Department of Natural Resources in cooperation with the U. S. Geological Survey, developed DOQs based on 1999 NAPP imagery and second generation of 10-meter DEMs. The 1999 DOQs are developed in two coordinate systems, UTM and the State Plane, referenced to North American Datum of 1983 (NAD83) with coordinates published both in meters and feet.
State Plane headers are available in feet under the directory called feet.  Each 1999 COQ (3.5 minute quarter-quadrangle, 1-meter ground resolution, 1:12,000 scale) requires about 2MB to 3MB of storage space. The transmission of coverage may take 25 minutes or more at 56KB and low-speed Internet links. The transmission of data at lower speeds is not recommended.
The 1993 COQs, (3.5 minute, quarter-quadrangle, 1-meter, 1:12,000 scale) are available on-line in NAD 83 and UTM projections. These COQs are accessible over the Internet through the Nebraska Department of Natural Resources website, and as well as its FTP site. Following options are available to retrieve COQs
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