U.S. Geological Survey
2010
EAARL Coastal Topography--Maryland and Delaware, post-Nor'Ida, 2009
first
remote-sensing image
U.S. Geological Survey Data Series
562
St. Petersburg, FL
U.S. Geological Survey
A digital elevation model (DEM) mosaic of a portion of the eastern Maryland and Delaware coastline, post-Nor'Ida (November 2009 nor'easter), was produced from remotely sensed, geographically referenced elevation measurements by the U.S. Geological Survey (USGS). Elevation measurements were collected over the area 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 50 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 +/-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.
The purpose of this project was to produce highly detailed and accurate digital elevation maps of a portion of the eastern Maryland and Delaware coastline, post-Nor'Ida (November 2009 nor'easter), for use as a management tool and to make these data available to natural-resource managers and research scientists.
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 terms first surface and bare earth refer to the digital elevation data of the terrain, but while the first-surface data include vegetation, buildings, and other manmade structures, the bare-earth data do not. The zero crossing of the second derivative (that is, detection of local maxima) 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 (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, fs_e123_n4567_18).
20091128
20091130
ground condition
None planned
ISO 19115 Topic Category
elevation
General
Airborne Lidar Processing System
ALPS
Digital Elevation Model
DEM
EAARL
Experimental Advanced Airborne Research Lidar
laser altimetry
lidar
remote sensing
topography
General
Maryland
Delaware
General
First Surface
General
2009
Post-Nor'Ida
None
The U.S. Geological Survey requests to be acknowledged as the originator of these data in future products or derivative research.
Amar Nayegandhi
Jacobs Technology, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Remote Sensing Specialist/Project Manager
mailing and physical address
600 4th Street South
St. Petersburg
FL
33701
USA
727 803-8747 (x3026)
727 803-2032
anayegandhi@usgs.gov
M-F, 9:00-5:00 EST
Acknowledgment of the U.S. Geological Survey, 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 U.S. Geological Survey 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 XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.2.2.1350
4.9000 E+5
4.9600 E+5
4.29600 E+6
4.24000 E+6
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, 3 centimeters nominal ranging accuracy, and vertical elevation accuracy of +/-15 centimeters for the topographic surface. Quality checks are built into the data-processing software.
Each file that was used to create this mosaic 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, fs_e123_n4567_18).
Several regions of the dataset are labeled as "No Data," which corresponds to a cell value of -32767 meters in the GeoTIFF file. These "No Data" areas are a result of the survey not covering a particular region, optical water depth of greater than 1.5 Secchi disc depths, or the manual removal of lidar processing artifacts. The presence of "No Data" values does not necessarily indicate an absence of land, but rather an absence of survey coverage or the presence of prolific vegetation that the laser is not able to penetrate in order to return bare-earth data.
Raw elevation measurements have been determined to be within 1 meter in horizontal accuracy.
Typical vertical elevation accuracies for these data are consistent with the point elevation data, +/-15 centimeters. However, a ground-control survey is not conducted simultaneously with every lidar survey. Vertical accuracies may vary based on the type of terrain and the accuracy of the GPS and aircraft-attitude measurements.
The data were collected using a Pilatus PC-6 aircraft. The Experimental Advanced Airborne Research Lidar (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 U.S. Geological Survey office in St. Petersburg, FL. The navigational data are processed and, along with the raw data, are downloaded into ALPS, or the Airborne Lidar Processing System (20091231 - 20100716). Data are converted from units of time to x,y,z points for elevation and formatted into .las and .xyz files. The derived surface data can then be converted into raster data (GeoTIFFs).
20091128 through 20100716
Jamie M. Bonisteel-Cormier
Jacobs Technology, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Lidar Analyst
mailing and physical address
600 4th Street South
St. Petersburg
FL
33701
USA
727 803-8747 (x3124)
jcormier@usgs.gov
M-F, 8:00-4:00 EST
Metadata imported into ArcCatalog from XML file.
20101021
Emily Klipp
Jacobs Technology, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Data Analyst II
mailing and physical address
600 4th Street South
St. Petersburg
FL
33701
USA
727 803-8747 (x3089)
eklipp@usgs.gov
M-F, 9:00-5:00 EST
Tiling Index
Raster
Pixel
Universal Transverse Mercator
18
0.999600
-75.000000
0
500000.000000
0
row and column
2.500000
2.500000
meters
North American Datum of 1983
Geodetic Reference System 80
6378137.000000
298.25722210100002
North American Vertical Datum of 1988
0.15
meters
Explicit elevation coordinate included with horizontal coordinates
Each pixel of the encoded GeoTIFF has an explicit elevation value associated with it. The GeoTIFF grid is encoded with a 2.5-meter resolution. The input parameters for the random consensus filter (RCF) were: grid cell size (buffer) = 6 meters x 6 meters; vertical tolerance (vertical width) = 500 centimeters for first surface and 50 centimeters for bare earth. The GeoTIFFs were created using Delauney triangulation, followed by linear interpolation based on the routines in the ITT VIS Interactive Data Language (IDL) code.
https://pubs.usgs.gov/of/2009/1078/
U.S. Geological Survey
Amar Nayegandhi
Project Manager
mailing and physical address
600 4th Street South
St. Petersburg
FL
33701
USA
727 803-8747 (x3026)
M-F, 9:00-5:00 EST
DS 562
This DVD publication was prepared by an agency of the United States Government. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, 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 U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and/or contained herein. Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights.
GeoTIFF
GeoTIFF
2
DVD
DVD
Vary
Contact U.S. Geological Survey.
Vary
Contact U.S. Geological Survey for details.
20091128
20091130
20110105
Xan Fredericks
Jacobs Technology, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
GIS Analyst/Metadata Specialist
mailing and physical address
600 4th Street South
St. Petersburg
FL
33701
USA
727 803-8747 (x3086)
afredericks@usgs.gov
M-F, 8:00-4:00 EST
FGDC Content Standards for Digital Geospatial Metadata
FGDC-STD-001-1998
local time