2010 USGS/NASA Experimental Advanced Airborne Research Lidar (EAARL): Chandeleur Islands, Louisiana (Bare-Earth)
This kmz file shows the extent of coverage of the 2010 USGS Chandeleur Islands, LA lidar data set.
A bare-earth digital elevation map (also known as a Digital Elevation Model, or DEM) of a portion of the Chandeleur Islands, Louisiana, was produced from remotely sensed, geographically referenced elevation measurements cooperatively by the U.S. Geological Survey (USGS) and the National Aeronautics and Space Administration (NASA). Elevation measurements were collected over the area using the NASA Experimental Advanced Airborne Research Lidar (EAARL), a pulsed laser ranging system mounted onboard an aircraft to measure ground elevation, vegetation canopy, and coastal 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 target area at approximately 50 meters per second at an elevation of approximately 300 meters. The EAARL, developed by NASA at Wallops Flight Facility in Virginia, measures ground elevation with a vertical resolution of +/-15 centimeters. A sampling rate of 3 kilohertz or higher results in an extremely dense spatial elevation dataset. Over 100 kilometers of coastline can be surveyed easily within a 3- to 4-hour mission. When subsequent elevation maps for an area are analyzed, they provide a useful tool to make management decisions regarding land development.
|Other Access||Online access information not available.|
|Distributor||DOC/NOAA/NOS/OCM > Office for Coastal Management, National Ocean Service, National
Oceanic and Atmospheric Administration, U.S. Department of Commerce
|Dataset Point of Contact||Amar Nayegandhi
Jacobs Technology, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
727 803-8747 (x3026)
Documentation links not available.
|Data Presentation Form:|| Digital image
|Dataset Progress Status||Complete|
|Data Update Frequency:||Not planned|
The variables measured by EAARL are distance between aircraft and GPS satellites (meters), attitude information
(roll, pitch, heading in degrees), scan angle (degrees), second of the epoch (seconds), and 1-nanosecond time-resolved return intensity
waveform (digital counts). Raw lidar data are not in a format that is generally usable by resource managers and scientists for scientific analysis.
Converting dense lidar elevation data into a readily usable format without loss of essential information requires specialized processing.
The U.S. Geological Survey's Coastal and Marine Geology Program (CMGP) has developed custom software to convert raw lidar data into a
GIS-compatible map product to be provided to GIS specialists, managers, and scientists. The primary tool used in the conversion process
is Airborne Lidar Processing System (ALPS), a multi-tiered processing system developed by a USGS-NASA collaborative project. Specialized
processing algorithms are used to convert raw waveform lidar data acquired by the EAARL to georeferenced spot (x,y,z) returns
for "first surface" and "bare earth" topography. The zero crossing of the second derivative (that is, detection of local maxima) is used
to detect "first surface" topography, while the trailing edge algorithm (that is, the algorithm searches for the location prior to the
last return where direction changes along the trailing edge) is used to detect the range to the last return or "bare earth." Statistical
filtering, known as the Random Consensus Filter (RCF), is used to remove false bottom returns and other outliers from the EAARL topography
data. The filter uses a grid of non-overlapping square cells (buffer) of user-defined size overlaid onto the original point cloud. The
user also defines the vertical tolerance (vertical width) based on the topographic complexity and point-sampling density of the data.
The maximum allowable elevation range within a cell is established by this vertical tolerance. An iterative process searches for the
maximum concentration of points within the vertical tolerance and removes those points outside of the tolerance (Nayegandhi and others, 2009).
These data are then converted to the North American Datum of 1983 and the North American Vertical Datum of 1988 (using the GEOID09 model).
Each file contains data located in a 2-kilometer by 2-kilometer tile, where the upper-left bound can be assessed quickly through the filename.
The first 3 numbers in the filename represent the left-most UTM easting coordinate (e###000) in meters, the next 4 numbers represent the
top-most UTM northing coordinate (n####000) in meters, and the last 2 numbers (##) represent the UTM zone in which the tile is located
(for example, be_e123_n4567_16). The development of custom software for creating these data products has been supported by the U.S.
Geological Survey CMG Program's Decision Support for Coastal Parks, Sanctuaries, and Preserves project. Processed data products are used
by the U.S. Geological Survey CMG Program's National Assessments of Coastal Change Hazards project to quantify the vulnerability of
shorelines to coastal change hazards such as severe storms, sea-level rise, and shoreline erosion and retreat.
|Purpose:||The purpose of this project was to produce highly detailed and accurate bare-earth digital elevation maps of a portion of the Chandeleur Islands, Louisiana, for use as a management tool and to make these data available to natural-resource managers and research scientists.|
|Time Period:||Unknown to Unknown|
|Spatial Reference System:||urn:ogc:def:crs:EPSG::4269|
|Spatial Bounding Box Coordinates:||
|Spatial Coverage Map:|
|Use Constraints||No constraint information available|
|Fees||Fee information not available.|
Last Modified: 2013-05-09
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