USGS Western Region
National DOQ Program (NDOP)
DOQ Points of Contact
8-meter resolution portion of a 3.75-minute DOQ
1-meter resolution portion of a 3.75-minute DOQ
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DOQ Fact Sheet
GeoTIFF Format Specification
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|What is a DOQ?
An aerial photograph and an orthophoto or orthoimage may look alike, but there are several important differences that allow an orthophoto to be used like a map. A conventional perspective aerial photograph contains image distortions caused by the tilting of the camera and terrain relief (topography). It does not have a uniform scale. You cannot measure distances on an aerial photograph like you can on a map. An aerial photo is not a map. The effects of tilt and relief are removed from the aerial photograph by a mathematical process called rectification. An orthophoto is a uniform-scale image. Since an orthophoto has a uniform scale, it is possible to measure directly on it like other maps. An orthophoto may serve as a base map onto which other map information may be overlain. A DOQ can be used on-screen to collect, review, and revise other digital data, especially digital line graphs (DLG) and topographic maps. When the DOQ is combined with other digital products, such as digital raster graphics (DRG) or digital elevation models (DEM), the resulting image provides additional visual information for the extraction and revision of base cartographic information.
How to Obtain DOQs
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Page Last Modified: Tuesday, 24-Sep-2013 10:11:59 EDT (alv)