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Lidar for Science and Resource Management

Lidar Topography Mapping in National Parks

The U.S. Geological Survey (USGS) Coastal and Marine Geology Program (CMGP) has been collaborating with the National Aeronautics and Space Administration (NASA) and the National Park Service (NPS) to acquire dense lidar topographic data in a variety of coastal environments. The Experimental Advanced Airborne Lidar (EAARL) system used in this data acquisition effort is uniquely suited to capturing sub-aerial and submerged topography in the same overflight. The voluminous data sets acquired from the EAARL surveys are processed using a Linux-based, custom-built system, Airborne Lidar Processing System (ALPS), developed in a NASA-USGS collaboration. This processing system enables the systematic creation of highly detailed submarine and sub-aerial topographic maps for use in ecological models and environmental stewardship.

The National Park Service, through itís Inventory and Monitoring (I&M) Program is mandated to "improve park management through greater reliance on scientific knowledge." Accordingly, a primary role of the NPS I&M Program is to collect, organize, and make available natural resource data and to contribute to the Service's institutional knowledge by facilitating the transformation of data into information through analysis, synthesis, and modeling.

The USGS CMGP is currently collaborating with three of the 32 networks of the NPS I&M Program:

Lidar data acquired in collaboration with these networks are being used to inventory and monitor marine benthic communities, barrier island geomorphology and vegetated habitats along coastlines for National Parks.

Coral reef communities within the SFCN represent some of the best Caribbean and Western Atlantic Coral reefs within the National Park Service. One objective of the USGS-NPS collaborative research is to create techniques to survey coral reefs for the purposes of habitat mapping, ecological monitoring, change detection, and event assessment (for example: bleaching, hurricanes, and disease outbreaks). Detailed submerged topographic maps of portions of the Florida reef tract within Biscayne National Park (BISC), and Dry Tortugas National Park (DRTO) (fig. 1) have enabled the characterization of benthic communities and monitoring of reef health. Shallow benthic habitats in the Virgin Islands National Park (VIIS) and Buck Island Reef National Monument (BUIS) were surveyed in 2004 using the EAARL system. Full-island sub-aerial topography and surrounding shallow bathymetry of St. John, VI enabled the creation of a seamless topo-bathy mosaic (fig. 2).

Submerged Topography map at Dry Tortugas National Park
Figure 1. Submerged Topography map at Dry Tortugas National Park. [larger version]
Mosaic of 2003 St. John EAARL first-surface and submerged topography
Figure 2. Mosaic of 2003 St. John EAARL first-surface and submerged topography. [larger version] [OFR 2006-1244]

Changes in coastal geomorphic features including dunes, cliffs, shorelines and edge of vegetation along barrier islands of the northeast Atlantic coast are being monitored using repeat lidar surveys in a close collaboration with NPS NCBN. High-resolution topographic data and color-infrared (CIR) imagery have been acquired and processed to create recent sedimentary environment maps of the barrier island geomorphology and vegetated habitats at Assateague Island National Seashore (ASIS; fig. 3). Repeat lidar surveys at Fire Island National Seashore (FIIS) and the Sandy Hook unit of Gateway National Recreation Area (GATE) have been used to determine net volumetric change following major storm events.

Recent Sedimentary Environments map at Assateague Island National Seashore
Figure 3. Recent Sedimentary Environments map at Assateague Island National Seashore. [larger version] [Legend] [OFR 2007-1388]

In collaboration with NPS-GULN, EAARL-derived vegetation metrics are being used to provide reliable and consistent quantitative information on the physical structural characteristics of park vegetation resources at the larger-area and park/landscape level. Vegetation characteristics may be quantitatively addressed by measuring the structure, dimensions and locations of vegetation patches or units as physical objects. These patches of vegetation communities, derived using methodologies that are consistent and reproducible, can be coupled with CIR imagery and ground-truth data to derive taxonomic identification for a large-scale vegetation structural monitoring protocol.

Raw lidar data are not in a format that is generally usable by National 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 USGS converts raw lidar data into a Geographic Information Systems (GIS)-compatible map products to be provided to National Park Service GIS specialists, managers, and scientists. The primary tool used in the conversion process is ALPS, a multi-tiered processing system developed by a USGS-NASA collaboration for the use of topographic lidar in coastal change assessment. Specialized processing algorithms are used to convert raw waveform lidar data acquired by the EAARL to georeferenced spot (American Standard Code for Information Interchange (ASCII) xyz) returns for first-surface and bare-Earth topography. These data are then converted to the North American Datum (NAD)83 horizontal and North American Vertical Datum (NAVD)88 vertical datum (using the GEOID03 model). The final products are 2-km by 2-km map tiles written out in a standard Georeferenced Tagged Image File Format (GeoTIFF) with associated metadata information. These tiles are created for visual interpretation and regional quantitative analysis. Metadata files include the standard Federal Geographic Data Committee (FGDC) format.

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