2007 USGS/NPS/NASA Experimental Advanced Airborne Research Lidar (EAARL): Naval Live Oaks Area, FL

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.

Original contact information:

Contact Name: David Nagle

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

Title: Programmer/Analyst

Phone: 727-803-8747 (x3093)

Email: dnagle@usgs.gov

The purpose of this project was to produce highly detailed and accurate digital elevation maps and CIR imagery of the Naval Live Oaks Area

in Florida's Gulf Islands National Seashore for use as a management tool and to make these data available to 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 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). The

"canopy height" can then be determined by subtracting the "bare earth" elevations from the "first surface" elevations. 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_16). Once the EAARL

topography data has been processed, the ALPS software can then use it with the raw geopositional and orientation data from the survey to

georeference color-infrared (CIR) imagery co-acquired alongside the lidar data. Each image is first roughly projected into coordinates using a

specialized processing algorithm (in ALPS) that incorporates information from the camera lens parameters, the raw data, and an estimated initial

elevation. The georeferencing is then iteratively improved by using the lidar elevation data in the algorithm until the solution stabilizes. This

georeferencing method creates a worldfile and projection file for each CIR image. Once the imagery has been assessed visually by an operator for

quality issues, the imagery and associated data are then processed using commercial software to mosaic the images into seamless

25-centimeter-resolution images using the 2-kilometer by 2-kilometer tiling scheme described above.

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.

The ASPRS LAS grid is encoded with a 1 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.

See http://pubs.usgs.gov/of/2009/1078/

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

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/565/supplemental/2007_USGS_NPS_NASA_EAARL_Lidar_Naval_Live_Oaks.kmz

Any conclusions drawn from the analysis of this information are not the responsibility of 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, National Park Service, 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

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.

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.

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. fs_e123_n4567_16).