2010 USGS/NASA Experimental Advanced Airborne Research Lidar (EAARL): Chandeleur Islands,
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.
Cite this dataset when used as a source.
|Search and Download
|| Distributor information not available
| Point of Contact
Jacobs Technology, U.S. Geological Survey, St. Petersburg Coastal and Marine Science
Center, St. Petersburg, FL
727 803-8747 (x3026)
Documentation links not available.
- DOI/USGS > United States Geological Survey, U.S. Department of the Interior
|Data Presentation Form:
|| Digital image
|Dataset Progress Status
|Data Update Frequency:
|| Not planned
||The variables measured by EAARL are distance between aircraft and GPS satellites (meters),
(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.
||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.
|| Unknown to Unknown
|Spatial Reference System:
|Spatial Bounding Box Coordinates:
|Spatial Coverage Map:
- Airborne Lidar Processing System
- Digital Elevation Model
- Experimental Advanced Airborne Research Lidar
- laser altimetry
- remote sensing
- Northern Gulf of Mexico
- Chandeleur Islands
| Use Constraints
|| No constraint information available
|| Fee information not available.
|| Lineage statement not available.
- Jacobs Technology, U.S. Geological Survey, St. Petersburg Coastal and Marine Science
Center, St. Petersburg, FL
- DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department
| Processing Steps
- The data are collected using a Pilatus PC-6 aircraft. The NASA Experimental Advanced
Airborne Research Lidar (EAARL) laser scanner collects the data using a green (532-nanometers)
raster scanning laser, while a digital camera acquires a visual record of the flight.
The data are stored on hard drives and archived at the U.S. Geological Survey office
in St. Petersburg, Florida, and the NASA office at Wallops Flight Facility in Virginia.
The navigational data are processed at Wallops Flight Facility. The navigational and
raw data are then downloaded into the Airborne Lidar Processing System (ALPS). Data
are converted from units of time to x,y,z points for elevation. The derived surface
data can then be converted into raster data (GeoTIFFs).
- The NOAA Coastal Services Center received the data in LAS format. The files contained
Lidar elevation and intensity measurements. The data were projected in UTM coordinates
(NAD83; Zone 16N) and referenced to the North American Vertical Datum of 1988 (NAVD88)
using the Geoid09 model. The following processes were performed to make the data available
within the Digital Coast: 1. The data were converted from UTM (NAD83; Zone 16N) to
geographic coordinates (NAD83). 2. The data were converted from NAVD88 (orthometric)
heights to GRS80 (ellipsoidal) heights using the Geoid09 model. 3. The data were reclassified
to reflect the ASPRS LAS bare earth classification. 4. The LAS data were sorted by
latitude and the headers were updated.
- The NOAA National Geophysical Data Center (NGDC) received lidar data files via ftp
transfer from the NOAA Coastal Services Center. The data are
currently being served via NOAA CSC Digital Coast at http://www.csc.noaa.gov/digitalcoast/.
The data can be used to re-populate the system. The data are archived in LAS
or LAZ format. The LAS format is an industry standard for LiDAR data developed by
the American Society of Photogrammetry and Remote Sensing (ASPRS); LAZ is a loseless
compressed version of LAS developed by Martin Isenburg (http://www.laszip.org/). The
data are exclusively in geographic coordinates (either NAD83 or ITRF94). The data
are referenced vertically to the ellipsoid (either GRS80 or ITRF94), allowing for
the ability to apply the most up to date geoid model when transforming to orthometric
Metadata Last Modified: 2013-05-09
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