2004 USGS/NASA Experimental Advanced Airborne Research Lidar (EAARL): Northern Gulf of Mexico, Post-Hurricane Ivan

ASCII xyz point cloud data were produced from remotely-sensed, geographically-referenced elevation measurements in cooperation with the

U.S. Geological Survey (USGS) and National Air 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 kHz or higher results in an extremely dense spatial elevation data set.

Over 100 kilometers of coastline can be easily surveyed within a 3 to 4 hour mission time period. 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 or John Brock at USGS

Contact Org: Jacobs Technology, contracted to USGS

Title: Computer Scientist

Phone: 727-803-8747

Email: anayegandhi@usgs.gov

The ASCII elevation data can be used to create raster Digital Elevation Models (DEMs). The purpose of this project is to produce highly

detailed and accurate digital elevation maps of the post Hurricane Ivan data for use as a management tool and to make this data available

to natural resource managers and research scientists.

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Raw lidar data is not in a format that is generally usable by resource managers and scientists. 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 (CMG) Program 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 Advanced 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. These data

are then converted to the North American Datum of 1983 and the North American Vertical Datum of 1988 (using the Geoid 03 model).

The files are in the Quarter Quad tiling format and the exact tile location is contained in the filename at n88_########_mf_be where #######

is the Quarter Quad tile ID.

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/geoid18/1123/supplemental/2004_USGS_NASA_EAARL_Lidar_Northern_Gulf_Post_Hurricane_Ivan.kmz

LAS

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 1ns 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, NASA, the Office for Coastal Management

or its partners.

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.

The U.S. Geological Survey and National Aeronautics and Space Administration request to be acknowledged as originators of this data in future

products or derivative research.

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

The expected accuracy of the measured variables are as follows: attitude within 0.07 degree, 3 cm nominal laser 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.

Several regions of the dataset are labeled as "No Data", which corresponds to a cell value of -32767 m 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 files are in the Quarter Quad tiling format and the exact tile location is contained in the filename at n88_########_mf_be where ####### is

the Quarter Quad tile ID. See QQ_naming_convention.doc in the 'extras' directory.