U.S. Geological Survey
20170324
EAARL Coastal Topography--Northern Assateague Island National Seashore, Maryland and Virginia, 2003: Bare Earth
first
raster digital data
U.S. Geological Survey Data Release
doi:10.5066/F7PV6HKJ
St. Petersburg, FL
U.S. Geological Survey
https://doi.org/10.5066/F7PV6HKJ
A bare-earth topography Digital Elevation Model (DEM) mosaic for the northern half of Assateague Island National Seashore was produced from remotely sensed, geographically referenced elevation measurements acquired cooperatively by the U.S. Geological Survey (USGS) and the National Park Service (NPS). Elevation measurements were collected over northern Assateague Island National Seashore using the first-generation National Aeronautics and Space Administration (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 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 the Assateague Island National Seashore in Maryland and Virginia, 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), 03LTS05. Additional survey and data details are available at http://cmgds.marine.usgs.gov/fan_info.php?fan=03LTS05.
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. 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 and the North American Vertical Datum of 1988 (Geoid 99).
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.
20030225
ground condition
None planned
USGS Metadata Identifier
USGS:03a70323-f8e0-47a0-9360-02df9a6ea6cf
ISO 19115 Topic Category
elevation
None
Airborne Lidar Processing System
ALPS
EAARL
Experimental Advanced Airborne Research Lidar
laser altimetry
lidar
remote sensing
topography
USGS National Assessment Project
Digital Elevation Model
DEM
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
Maryland
Virginia
Assateague Island
Atlantic Ocean
None
Bare earth
None
2003
None
The U.S. Geological Survey requests to be acknowledged as originator of these data in future products or derivative research.
Christine Kranenburg
Cherokee Nation Technologies, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Computer Scientist
mailing and physical address
600 4th Street South
St. Petersburg
FL
33701
USA
727 502-8129
727 502-8182
ckranenburg@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
-75.247162
-75.092258
38.325816
38.055486
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 are as follows: attitude within 0.07 degree, 3-cm nominal ranging accuracy, and vertical elevation accuracy of +/-15 cm for the topographic surface. Quality checks are built into the data-processing software.
These data were processed for topography ONLY.
Missing areas are represented by a "no data" value of -32,767 and are a result of the survey not covering a particular region, automated filtering or automated clipping to the official NPS 2003 park boundary polygon for Assateague Island National Seashore.
Raw elevation measurements have been determined to be within 1 meter in horizontal accuracy.
Point elevation measurements from the EAARL system have been determined to be within +/- 15 cm in vertical accuracy; however, a ground-control survey was not completed simultaneously with this lidar survey.
The data were collected using a Cessna 310 aircraft. 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 (20030710), interactively processed small sections of the data to obtain best estimates of aircraft pitch and roll biases.
20030710
Amar Nayegandhi
ETI Professionals, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Computer Scientist
mailing and physical address
600 4th Street South
St. Petersburg
FL
33701
USA
727-502-8129
eaarl-meta@usgs.gov
M-F, 8:00-4:00 ET
ALPS (20030710-20040401) was used to batch process the raw data for first and last return topography. Next, it batch filtered the point cloud using the interactive RCF. The input parameters of the RCF were: grid cell size (buffer) = 400 cm x 400 cm; vertical tolerance (vertical width) = 50 cm. The data were also datum converted from ITRF00 to NAD83, NAVD88 using the Geoid99 model.
20040401
Amar Nayegandhi
ETI Professionals, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Computer Scientist
Physical and Mailing
600 4th Street South
St. Petersburg
FL
33701
USA
727-502-8129
eaarl-meta@usgs.gov
The final .pbd (Portable Data Base) format files were loaded into ALPS (20170223) to remove any data from the tile buffers and merge them into a single product, which was then exported as a gridded raster data (GeoTIFF) format. Tile buffers are an overlap region extending 200 meters past the edges of the 2-Km tile and contain duplicate data from adjacent tiles. The GeoTIFF is created using Delauney triangulation of the lidar point data to create a triangulated irregular network (TIN), followed by linear interpolation at the pixel center coordinates to said TIN. The tinning and interpolation are performed by routines implemented in the Harris Geospatial Interactive Data Language (IDL) code. The GeoTIFF grid, which is provided at a 2.5-meter horizontal resolution, is encoded with the interpolated elevation value. Finally, the raster data were clipped to the boundary of the NPS 2003 Assateague Island polygon.
20170223
Christine Kranenburg
Cherokee Nation Technologies, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Computer Scientist
Physical and Mailing
600 4th Street South
St. Petersburg
FL
33701
USA
727-502-8129
ckranenburg@usgs.gov
Added keywords section with USGS persistent identifier as theme keyword.
20201013
U.S. Geological Survey
VeeAnn A. Cross
Marine Geologist
Mailing and Physical
384 Woods Hole Road
Woods Hole
MA
02543-1598
508-548-8700 x2251
508-457-2310
vatnipp@usgs.gov
raster
Pixel
Universal Transverse Mercator
18N
0.999600
-75.000000
0.000000
500000.000000
0.000000
row and column
2.5
2.5
meters
North American Datum of 1983
Geodetic Reference System 80
6378137.000000
298.257222
North American Vertical Datum of 1988
0.001 m
meters
Explicit elevation coordinate included with horizontal coordinates
Each pixel of the encoded GeoTIFF has an explicit elevation value associated with it.
http://pubs.usgs.gov/of/2009/1078/
Christine Kranenburg
Cherokee Nation Technologies, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Computer Scientist
Physical and Mailing
600 4th Street South
St. Petersburg
FL
33701
USA
727-502-8129
ckranenburg@usgs.gov
ASIS2003_EAARLA_BE_z18_n88g99_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
GeoTIFF
2
http://coastal.er.usgs.gov/data-release/doi-F7PV6HKJ/data/ASIS2003_EAARLA_BE_z18_n88g99_mosaic.zip
Available Online
None, if obtained online.
20201013
Christine Kranenburg
Cherokee Nation Technologies, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Computer Scientist
Physical and Mailing
600 4th Street South
St. Petersburg
FL
33701
USA
(727) 502-8129
ckranenburg@usgs.gov
FGDC Content Standards for Digital Geospatial Metadata
FGDC-STD-001-1998
local time