2003 U.S. Geological Survey (USGS) Experimental Advanced Airborne Research Lidar (EAARL): US Virgin Islands (St. John, St. Croix)

This data set contains topographic and bathymetric lidar data that were collected on April 21, 23, 30, May 2, and June 14, 17 of 2003,

cooperatively by the U.S. Geological Survey (USGS), National Aeronautics and Space Administration (NASA), and National Park Service (NPS).

The data is for part of the U.S. Virgin Islands (island of St. John and a portion of the northern coastline of St. Croix). The bathymetric lidar

data are classified as 11 and the topographic lidar data are classified as 0.

A first surface and submerged topography elevation map (also known as a Digital Elevation Model, or DEM) of a portion of the U.S. Virgin Islands

(island of St. John and a portion of the northern coastline of St. Croix) was produced from remotely sensed, geographically referenced

elevation measurements cooperatively by the U.S. Geological Survey (USGS), National Aeronautics and Space Administration (NASA), and National

Park Service (NPS).

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.

Original contact information:

Contact Name: Amar Nayegandhi

Contact Org: Jacobs Technology, U.S. Geological Survey, FISC, St. Petersburg, FL

Title: Computer Scientist

Phone: 727-803-8747 (x3026)

Email: anayegandhi@usgs.gov

The purpose of this project was to produce a highly detailed and accurate first surface and submerged topography elevation map of a portion

of the U.S. Virgin Islands.

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Raw Lidar data are not in a format that is generally usable by Park Service 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 converts raw Lidar data into a GIS-compatible map product to be provided to National Park Service 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 development of custom software for creating these data products has been supported by the USGS CMG Program's Decision Support for

Coastal Parks, Sanctuaries, and Preserves Project. Processed data products are used by the USGS 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.

A footprint of this data set may be viewed in Google Earth at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/566/supplemental/2003_USGS_USVI_TopoBathy_Lidar.kmz

Each pixel of the encoded GeoTIFF has an explicit elevation value associated with it. The GeoTIFF grid is encoded with a 1-meter resolution.

The variables measured by EAARL are distance between aircraft and GPS satellites (m), attitude information (roll, pitch, heading in

degrees), scan angle (degrees), second of the epoch (sec), and 1-ns time-resolved return intensity waveform (digital counts). Z value is

referenced to orthometric elevations derived from National Geodetic Survey Geoid Model, GEOID03.

Any conclusions drawn from the analysis of this information are not the responsibility of the USGS, the Office for Coastal Management or its partners.

Unclassified

None

This data can be obtained on-line at the following URL: https://coast.noaa.gov/dataviewer;

None

Users should be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no

longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its

limitations.

Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.2.2.1350

The expected accuracy of the measured variables is 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.

Raw elevation measurements have been determined to be within 1-meter horizontal accuracy.

Elevations of the DEM are vertically consistent with the point elevation data, +/-15 cm.

Not Provided

When the data was received by the NOAA Office for Coastal Management, each file contained data located in a 2-km by 2-km tile, where the upper-left

bound can be quickly assessed through the file name. The first 3 numbers in the file name represented the left-most UTM easting coordinate

(e###000) in meters, the next 4 numbers represented the top-most UTM northing coordinate (n####000) in meters, and the last 2 numbers (##)

represented the UTM zone in which the tile is located (for example, fs_e123_n4567_20).