Published By Federal Emergency Management Agency, Department of Homeland Security
Issued over 9 years ago
Summary
Description
The aerial image files in this archive are copies of standard digital orthophoto quadrangles (DOQ) from the National Digital Cartographic Data Base that have been repositioned to the Michigan GeoRef coordinate system. Orthophotographs represent aerial images where the perspective view of the camera is corrected to fit the geometry of a flat map. During the rectification process, the images are referenced to a particular cartographic projection system. This enables the user to display the images next to each other in their correct geographic location, map features directly from the image, or display other map information directly over the image. DOQs represent an orthorectified image product that meets a particular set of specifications developed by the U.S. Geological Survey (USGS). DOQ files are organized by the time period associated with film acquisition. Currently, DOQs in Michigan have been produced from two statewide flights that were initiated in 1992 and 1998 under the National Aerial Photography Program (NAPP) administered by USGS. Generally, production work terminates on an image series when a new flight is completed. Acquisition cycles are five to seven years apart. A complete description of DOQs is available from the USGS Web site.