2001 USGS/NASA Airborne Topographic Mapper (ATM) Lidar: Coastal Alabama, Florida, Louisiana, Mississippi, Texas

This is a non-bare earth data set. ASCII xyz point cloud data were produced from remotely sensed, geographically referenced elevation

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

of Alabama, Florida (Panhandle), Louisiana, Mississippi and Texas in 2001.

Dates of collection are:

1. Alabama 20011002-20011004, 20011007-20011010

2. Florida 20011002

3. Louisiana 20010909-20010910

4. Mississippi 20010909-20010910

5. Texas 20011012-20011013

Elevation measurements were collected over the area using the NASA Airborne Topographic Mapper (ATM), a scanning Lidar system that measures

high-resolution topography of the land surface. The ATM system is deployed on a Twin-Otter or P-3 Orion aircraft and incorporates a

green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser ranging device are coupled with data

acquired from internal navigation system (INS) attitude sensors and differentially-corrected global positioning system (GPS) receivers to

measure topography of the surface at accuracies of 10 to 20 centimeters.

Original contact information:

Contact Name: Amar Nayegandhi

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

Title: Computer Scientist

Phone: 727-803-8747 (x3026)

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 elevation maps of the Alabama, Florida (Panhandle), Louisiana, Mississippi, and Texas coastlines for natural

resource managers and research scientists.

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Raw Lidar data are 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 GEOID03 model).

The files are in the Quarter-Quad tiling format and the exact tile location is contained in the filename at ########_fs, 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.

Binary lidar data file for xyz data points.

The variables measured by the ATM 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 NOAA, the Office for Coastal Management or its partners.

This data 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 herein 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.

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 ArcMap 9.2.2.1350

The expected accuracy of the measured variables is 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". 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 file name at ########_fs, where ####### is

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