| Description |
Elevation maps (also known as Digital Elevation Models or DEMs) of Colonial National Historical Park were produced from remotely-sensed, geographically-referenced elevation measurements in cooperation with NASA and NPS. Point data in ASCII text files were interpolated in a GIS to create a grid or digital elevation model (DEM) of each surface. Elevation measurements were collected in Virginia, over Colonial National Historical Park, using the NASA Experimental Advanced Airborne Research Lidar (EAARL), a pulsed laser ranging system mounted onboard an aircraft to measure ground elevation and topography. The system uses high frequency laser beams directed at the earth's surface through an opening in the bottom of the aircraft's fuselage. The laser system records the time difference between emission of the laser beam and the reception of the reflected laser signal in the aircraft. The plane travels over the area at approximately 60 meters per second while surveying the base areas of the park. The EAARL, developed by the National Aeronautics and Space Administration (NASA) located at Wallops Flight Facility in Virginia, measures ground elevation with a vertical resolution of 15 centimeters. A sampling rate of 3 kHz or higher results in an extremely dense spatial elevation data set. Over 100 kilometers can easily be surveyed within a 3- to 4-hour mission time period. The ability to sample large areas rapidly and accurately is especially useful in morphologically dynamic areas. For more information on Lidar science and the Experimental Advanced Airborne Research Lidar (EAARL) system and surveys, see http://ngom.usgs.gov/dsp/overview/index.php and http://ngom.usgs.gov/dsp/tech/eaarl/index.php . [More]
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