| Maryland Department of Natural Resources requested the collection of LIDAR data over
Kent, Queen Anne and Caroline Counties, MD. In response, EarthData acquired the data
from March 18 through April 6, 2006. Airborne lidar data was acquired at an altitude
of 5,500’(1676.4 m) above mean terrain with a swath width of 40’, which yields an
average post spacing of lidar points of no greater than 6.56 ft (2 m). The project
was designed to achieve a vertical accuracy of the lidar points at 7.09 in (18 cm)
root mean square error (RMSE). The flight design included a total of seventy-seven
flight lines with approximately 2,246 total line miles (3614.59 km). The lidar data
was acquired prior to the emergence of deciduous foliage. This is a bare earth data
set. Light Detection and Ranging (LIDAR) is a method of locating objects on the ground
using aerial-borne equipment. It is similar to RADAR or SONAR in that the two-way
travel time of an energy beam reflected off an object is precisely measured, but this
technology uses laser light instead of radio or sound waves. This technology has proven
very useful in remote sensing of the earth. It can be used for determining elevations
of both the earth’s surface and items (natural and man-made) on the surface. Analysis
of LiDAR data is used in detailed modeling of the earth’s surface for drainage and
floodplain studies, determining how a new structure will affect views from various
locations, shoreline erosion studies, and other reasons. "First returns" are the first
elevation value that the LiDAR sensor recorded for a given x,y coordinate. Likewise,
"last returns" are the last elevation value that the LiDAR sensor recorded for a given
x,y coordinate. The Bare Earth Mass Points are point elevations that represent the
"bare earth." Features that are above the ground - such as buildings, bridges, tree
tops, etc. - are not included in these data. The Gridded DEM is a model of the surface
of the earth (no above-surface features such as buildings, tree tops, etc) with a
point at every 2 meters representing the average surface elevation of that area. The
LIDAR Intensity Imagery are similar to aerial photography. While not as sharp as traditional
aerial photos, they offer a good visual representation of the surface and various
features.
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