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Digital OrthophotosWhat is a DOQ (Digital Orthophoto)? 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 overlaid (courtesy USGS).
What is the resolution of the
DOQs? 1 meters per pixel. |
