U.S. Geological Survey
20170807
EAARL Coastal Topography–Eastern Louisiana Barrier Islands Barrier Islands, 09 March 2008: First Surface
first
raster digital data
U.S. Geological Survey Data Release
doi:10.5066/F7M61HRQ
St. Petersburg, FL
U.S. Geological Survey
https://doi.org/10.5066/F7M61HRQ
A Digital Elevation Model (DEM) mosaic was data were produced from remotely sensed, geographically referenced elevation measurements by the U.S. Geological Survey (USGS). Elevation measurements were collected over some of the eastern Louisiana barrier islands in cooperation with the National Park Service (NPS), using the 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 60 meters per second at an elevation of approximately 300 meters, resulting in a laser swath of approximately 240 meters with an average point spacing of 2-3 meters. The EAARL, developed originally by NASA at Wallops Flight Facility in Virginia, measures ground elevation with a vertical resolution of 3 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 resultant elevation maps for an area are analyzed, they provide a useful tool to make management decisions regarding land development.
The purpose of this project was to provide highly detailed and accurate elevation data of coastal parks and barrier islands, post-Hurricane Katrina (August 2005 hurricane), for use as a management tool and to make these data available to natural-resource managers and research scientists. To ensure that St. Petersburg Coastal and Marine Science Center (SPCMSC) data management protocols were followed, this survey was assigned a USGS field activity number (FAN), 08LTS01. Additional survey and data details are available at https://cmgds.marine.usgs.gov/fan_info.php?fan=08LTS01.
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 USGS'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 originally 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 "first returns" are indicative of vegetation-canopy height, or bare ground in the absence of vegetation, whereas "last returns" typically represent "bare-earth" elevations under vegetation. The terms first surface and bare earth refer to the digital elevation data of the terrain, but while first-surface data include vegetation, buildings, and other manmade structures, bare-earth data do not. The zero crossing of the second derivative (that is, detection of stationary points) is used to detect the first return, resulting in "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" (the first and last returns being the first and last significant measurable portion of the return pulse). 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 (NAD83) and the North American Vertical Datum of 1988 (NAVD88) using the GEOID03 model.
The development of custom software for creating these data products has been supported by the USGS CMGP's Lidar for Science and Resource Management project. Processed data products are used by the USGS CMGP's National Assessment 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.
20080309
ground condition
None planned
-90.96659533
-89.42161120
29.35637844
29.00688973
ISO 19115 Topic Category
elevation
USGS Thesaurus
remote sensing
geomorphology
None
Airborne Lidar Processing System
ALPS
EAARL
Experimental Advanced Airborne Research Lidar
laser altimetry
lidar
topography
USGS National Assessment Project
digital elevation model
GeoTIFF (First Surface)
Global Change Master Science Directory
LAND SURFACE > TOPOGRAPHY > TERRAIN ELEVATION
OCEAN > COASTAL PROCESSES > BARRIER ISLANDS
OCEAN > COASTAL PROCESSES > BEACHES
OCEAN > COASTAL PROCESSES > SHORELINE DISPLACEMENT
DOI/USGS/CMG > COASTAL AND MARINE GEOLOGY, U.S. GEOLOGICAL SURVEY, U.S. DEPARTMENT OF INTERIOR
GCMD Instrument
LIDAR > LIGHT DETECTION AND RANGING
Geographic Names Information System
Louisiana
Gulf of Mexico
None
First Surface
None
2008
None
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey requests to be acknowledged as originator of these data in future products or derivative research.
Xan Fredericks
U.S. Geological Survey
mailing and physical address
600 4th Street South
St. Petersburg
FL
33701
USA
772 502-8086
727 502-8182
afredericks@usgs.gov
M-F, 8:00-4:00 ET
Acknowledgment of the USGS St. Petersburg Coastal and Marine Science Center, as a data source would be appreciated in products developed from these data, and such acknowledgment as is standard for citation and legal practices for data source is expected. Sharing of new data layers developed directly from these data would also be appreciated by the USGS staff. Users should be aware that comparisons with other datasets for the same area from other time periods may be inaccurate due to inconsistencies resulting from changes in photointerpretation, mapping conventions, and digital processes over time. These data are not legal documents and are not to be used as such.
Unclassified
Unclassified
None
Microsoft Windows 7 Version 6.1 (Build 7601) Service Pack 1; Esri ArcGIS 10.3.1.4959
Nayegandhi, A., Brock, J.C., and Wright, C.W.
2009
Small footprint, waveform-resolving lidar estimation of submerged and subcanopy topography in coastal environments
International Journal of Remote Sensing
30(4), p. 861-878
The expected accuracy of the measured variables is as follows: attitude within 0.07 degree and 3 centimeters nominal ranging accuracy. Quality checks are built into the data-processing software.
These data were processed for topography ONLY; offshore elevations are invalid.
These point-cloud data may appear sparse or nonexistent, which is a result of automated filtering or lack of survey coverage.
Raw elevation measurements have been determined to be within 1 meter in horizontal accuracy.
A ground-control survey is not conducted simultaneously with every lidar survey and vertical accuracies may vary based on the type of terrain and the accuracy of the Global Positioning System (GPS) and aircraft-attitude measurements.
The data were collected using a Cessna 310 aircraft (20080309). The EAARL laser scanner collects the data using a green-wavelength (532-nanometer) 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 USGS office in St. Petersburg, Florida. Raw EAARL waveform, GPS, and Inertial Measurement Unit (IMU) data were subsequently loaded into ALPS software. ALPS (20080602), interactively processed small sections of the data to obtain best estimates of aircraft pitch and roll biases. Pitch and roll biases are 0.3 and -1.64 respectively.
20080603
Xan Fredericks
U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
mailing and physical address
600 4th Street South
St. Petersburg
FL
33701
USA
772 502-8086
afredericks@usgs.gov
M-F, 8:00-4:00 ET
ALPS (20080604) was used to batch process the raw data for last return and first return topography. Next, it batch filtered the first surface topography using the RCF. The input parameters of the random consensus filter were: grid cell size (buffer) = 500 cm x 500 cm; vertical tolerance (vertical width) = 600 cm.
20080604
Xan Fredericks
U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Cartographer/Lidar Coordinator
Physical and Mailing
600 4th Street South
St. Petersburg
FL
33701
USA
(727) 502-8086
afredericks@usgs.gov
ALPS (20170302) was used to convert bare earth topography from the International Terrestrial Reference System of 2000 (ITRF00) to NAD83, NAVD88 using the GEOID03 model. Lastly, ALPS exported the NAD83, NAVD88 (GEOID03) first surface topography from .pbd format to a .tif file. Global Mapper v16.1 was used to create a mosaic .tif file.
20170302
Xan Fredericks
U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Cartographer/Lidar Coordinator
Physical and Mailing
600 4th Street South
St. Petersburg
FL
33701
USA
(727) 502-8086
afredericks@usgs.gov
Tiling Index
Raster
Pixel
1e-07
1e-07
Decimal degrees
North American Datum of 1983
Geodetic Reference System 80
6378137.000000
298.25722210100002
North American Vertical Datum of 1988 (GEOID03)
0.20
meters
Explicit elevation coordinate included with horizontal coordinates
Xan Fredericks
U.S. Geological Survey
Cartographer/Lidar Coordinator
Physical and Mailing
600 4th Street South
St. Petersburg
FL
33701
USA
(727) 502-8086
afredericks@usgs.gov
EasternLA2008_EAARLA_FS_n88g03_mosaic.tif
Although these data have been processed successfully on a computer system at the USGS, no warranty expressed or implied is made regarding the display or utility of the data on any other system, or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The USGS shall not be held liable for improper or incorrect use of the data described and/or contained herein. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
GeoTIFF
2
GeoTIFF
http://coastal.er.usgs.gov/data-release/doi-F7M61HRQ/data/EasternLA2008_EAARLA_FS_n88g03_mosaic.zip
Available Online
None
20170804
Xan Fredericks
U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Cartographer/Lidar Coordinator
Physical and Mailing
600 4th Street South
St. Petersburg
FL
33701
USA
(727) 502-8086
afredericks@usgs.gov
Content Standard for Digital Geospatial Metadata
FGDC-STD-001-1998
local time