remote-sensing image
U.S. Geological Survey2009EAARL Coastal Topography–Assateague Island National Seashore, 2008: Bare EarthfirstU.S. Geological Survey Data Series447St. Petersburg, FLU.S. Geological Survey
ASCII xyz point cloud data were produced from remotely sensed, geographically referenced elevation measurements cooperatively by the U.S. Geological Survey (USGS), the National Park Service (NPS), and 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 easily surveyed 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 a highly detailed and accurate bare-earth digital elevation map of the Assateague Island National Seashore in Virginia and Maryland 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 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 GEOID03 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 (ex. be_e123_n4567_18).
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.
en
2008032420080325
ground condition
None planned
4.8800 E+5
4.8600 E+5
4.22800 E+6
4.22600 E+6
Airborne Lidar Processing System
ALPShttp://remotesensing.usgs.govDigital Elevation ModelDEMEAARLExperimental Advanced Airborne Research Lidarlaser altimetryLidarremote sensingtopography
http://nationalmap.govAssateague Island National SeashoreVirginiaMaryland
http://lidar.cr.usgs.gov/Bare Earthhttp://www.esri.com/news/arcuser/1104/temporal.html2008
None
The U.S. Geological Survey, National Park Service, and National Aeronautics and Space Administration request to be acknowledged as originators of this data in future products or derivative research.
mailing and physical address
600 4th Street South
Saint Petersburg
FL
33701
USA
727-803-8747 (x3026)
M-F, 8:00-5:00 EST
Amar NayegandhiJacobs Technology, U.S. Geological Survey, FISC, St. Petersburg, FLanayegandhi@usgs.gov727-803-2031Computer Scientist
Acknowledgment of the U.S. Geological Survey, Florida Integrated Science Center, as a data source would be appreciated in products developed from these data, and such acknowledgement as is standard for citation and legal practices for data source is expected by users of this data. Sharing 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.
Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.2.2.1350
UnclassifiedUnclassifiedNone
The expected accuracy of the measured variables is as follows: attitude within 0.07 degree, 3-centimeter nominal ranging accuracy, and vertical elevation accuracy of +/-15 centimeters for the topographic surface. Quality checks are built into the data-processing software.
Raw elevation measurements have been determined to be within 1 meter in horizontal accuracy.
Elevations are vertically consistent with the point elevation data, +/-15 centimeters.
The data are collected using a Cessna 310 aircraft. The NASA Experimental Advanced Airborne Research Lidar (EAARL) laser scanner collects the data using a green (532-nm) 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).
Airborne Lidar Processing System
20080324 through 20080915mailing and physical address600 4th Street SouthSaint PetersburgFL33701USA727-803-8747 (x3026)M-F, 8:00-5:00 ESTComputer Scientistanayegandhi@usgs.govAmar NayegandhiJacobs Technology, U.S. Geological Survey, FISC, St. Petersburg, FL
GIS/Image Analyst/Metadata Specialistmailing and physical address600 4th Street SouthSt. PetersburgFL33701USA727-803-8747 (x3086)M-F, 8:00-5:00 ESTXan YatesJacobs Technology, U.S. Geological Survey, FISC, St. Petersburg, FLMetadata imported into ArcCatalog from XML file.ESRI ArcCatalog 9.2.2.135020080915Metadata imported.H:\Data_Series\ASIS\BE_metadata_LAStemp.xml2009050714200100
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 (ex. be_e123_n4567_18).Several regions of the dataset are labeled as "No Data". 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.
Point
row and column
1.000000
1.000000
meters
Universal Transverse Mercator18
North American Datum of 1983
Geodetic Reference System 80
6378137.000000
298.257222
GCS_North_American_1983
NAD_1983_UTM_Zone_18N
North American Vertical Datum of 1988
0.15
meters
Explicit elevation coordinate included with horizontal coordinates
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). Z value is referenced to orthometric elevations derived from National Geodetic Survey Geoid Model, GEOID03.
This raster represents Lidar-derived elevations.
The LAS grid is encoded with a 1 meter resolution. The input parameters for the Random Consensus Filter were: gird cell size (buffer) = 6 meters x 6 meters; vertical tolerance (vertical width) = 50 centimeters.
mailing and physical address
600 4th Street South
Saint Petersburg
FL
33701
USA
727-803-8747
U.S. Geological SurveyProject ManagerProject ManagerM-F, 8:00-5:00 EST
DS 447
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, nor shall the act of distribution imply 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. Reference herin to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.
VaryASCIIXYZ1DVDDVDContact U.S. Geological SurveyVary
Contact U.S. Geological Survey for details.
2008032420080325
20080915
mailing and physical address
St. Petersburg
FL
33701
600 4th Street SouthUSA
727-803-8747 (x3086)
Xan YatesJacobs Technology, U.S. Geological Survey, FISC, St. Petersburg, FLM-F, 8:00-5:00 ESTGIS/Image Analyst/Metadata Specialist
FGDC Content Standards for Digital Geospatial Metadata
FGDC-STD-001-1998
local time
en
http://www.esri.com/metadata/esriprof80.htmlESRI Metadata Profile
Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.2.2.1350
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3.81998676102073 E+1
3.81818135819887 E+1
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4.8800 E+5
4.22800 E+6
4.22600 E+6
4.8600 E+5
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ISO 19115 Geographic Information - Metadata
DIS_ESRI1.0
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20011Meter1 Meter = 1 Meter(s)20011Meter1 Meter = 1 Meter(s)