A GIS Application Example - National Park Service Inventory and Monitoring for Natural Resource Management
Tracking changes in terrain along coastal barrier island beaches requires accurate high-resolution topographic data. Traditional products, such as available contour maps or low- resolution digital elevation models (DEMs), could not provide the level of detail or the update frequency necessary to monitor barrier island parks. To address this need, the National Park Service and NASA initiated an experimental beach-mapping program using airborne lidar (light detection and ranging) high-resolution topographic surveys at Assateague Island National Seashore.
NASA began collecting airborne laser surveys over Assateague Island in 1995 using the NASA ATM sensor. Initially, the ATM carried a single-return green wavelength lidar; a down-looking camera was added in 2001. Further innovations in sensor development resulted in a new waveform-resolving green-wavelength lidar (NASA EAARL). The EAARL is a cross-environment sensor, capable of surveying both terrestrial and aquatic environments. Consequently, NASA lidar survey data provides a wide range of information, including but not limited to: 1) bare-earth digital elevation models, 2) first-return digital elevation models, and 3) vegetation canopy height and distribution. Currently, the EAARL system incorporates down-looking cameras for collecting digital photography in conjunction with the lidar survey data.
Data collected by the sensors are referenced to the ground using kinematic differential global positioning system (GPS) methods, providing vertical accuracy to within 20 cm. In addition, the orientation of the aircraft is measured using Inertial Navigation Systems (INS). Small laser spot size and high pulse frequency results in DEM products being produced at a 1-m resolution. The ATM and EAARL sensors are mounted on small aircraft and can be commissioned as needed. Typical flight time required to complete surveys within the NPS Northeast Coastal and Barrier Island network have varied between one to five days. As a result, lidar surveys not only provide accurate, high-resolution data sets, but can be acquired frequently in order to meet resource management and monitoring needs.
Over time, the project has developed to the point where survey data is being used in a number of park programs, including change detection for shorelines and the high resolution mapping of topography and bathymetry. Topographic lidar data and aerial photography acquired during NASA overflights of ASIS are being used in the Threatened and Endangered Species Recover Program1: Piping Plover and Sea Beach Amaranth, the Geomorphologic Monitoring Program1 (elevation models, topographic profiles, and beach re-nourishment), and within the Wildlife Management Program: Horse grazing effects on vegetation and natural dune evolution.
The project has also revealed the importance of the USGS/CCWS role in converting raw NASA remote sensing data sets into GIS-compatible information layers of high relevance to the management needs of National Seashores and Parks. Lidar surveys result in very large datasets, which in their raw format are not compatible with most GIS software. The USGS has taken the lead role in developing methods for processing these data to a level that can be imported into widely used GIS software packages. Data is presented to the park in ESRI compatible formats. As a result, parks have been able to directly access these data for use in park natural resource management activities.
Using lidar for change analysis on barrier islands. Monitoring dune volume change from 2 ATM lidar surveys conducted in 1998 and 2001 at Assateague Island National Seashore. [larger version] |
Using lidar to detect the shoreward edge of vegetation on barrier islands. This figure shows significant landward retreat of vegetation between 1999 and 2001 at Assateague Island National Seashore. [larger version] |
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