Overview

The USGS Coastal and Marine Geology Program (CMGP) is supporting the creation of new capabilities for the synoptic remote sensing of coastal-marine and terrestrial environments based on aircraft and satellite sensors.  Special emphasis has been placed on the use of aircraft-mounted light detection and ranging (lidar) and multi-spectral imaging to map coral reef ecosystem geomorphology, topographic roughness, and habitats at spatial scales finer than 2 m.  Through partnerships with the National Aeronautics and Space Administration (NASA), National Oceanic and Atmospheric Administration (NOAA), and National Park Service (NPS), these capabilities have been applied to create highly detailed benthic and submerged topography maps of portions of the Florida reef tract and the U.S. Virgin Islands.  In a similar collaboration between the USGS and NPS, aircraft lidar and color-infrared imaging have been acquired and processed to create high-resolution subaerial topographic maps of barrier island geomorphology and vegetated habitats for NPS Inventory and Monitoring Programs along the Northeast Atlantic and the Gulf Coast.

The Experimental Advanced Airborne Research Lidar (EAARL) system, used in many of these data-acquisition efforts, is a unique waveform-resolving, green-wavelength lidar system capable of mapping subaerial and submerged topography simultaneously. The EAARL sensor records the time history of the return waveform within a small footprint (20-cm diameter at nominal flying altitude of 300 m) for each laser pulse, enabling characterization of vegetation canopy structure and “bare-Earth” topography under a variety of vegetation types. EAARL surveys conducted over coastal-vegetation communities at Gulf Islands National Seashore and Jean Lafitte National Park were used to develop and evaluate the capability of lidar waveform data to determine the vertical distribution of canopy characteristics across a diverse set of vegetation classes. 

Post-processing of EAARL data is accomplished using a custom-built Airborne Lidar Processing System (ALPS) that combines laser return backscatter digitized at 1-nanosecond intervals with aircraft positioning data derived from an Inertial Measurement Unit and precision Global Positioning System (GPS) receivers. The ALPS software, developed in an open-source programming environment on a Linux platform through a NASA-USGS collaboration, enables the exploration and processing of lidar waveforms, and the creation of Digital Elevation Models (DEMs) for bare-Earth, canopy-top, and submerged topography. The ALPS software is also being used to process data acquired by the NASA Airborne Topographic Mapper (ATM). Continued development and maintenance of the ALPS software enables the creation of a wide range of topographic and other derived products from raw lidar data.

The broad usefulness of lidar surveys can be inhibited by the immensity of the data sets. Topographic products derived from lidar data are actively being used in ongoing studies of coastal change caused by both catastrophic storms and processes that operate over historical time scales. In order to make these data products suitable for map publication, a systematic manual editing and quality control review process is required. Further, the generation of these topographic map products enables the interpretation of recent sedimentary environments and other geomorphologic processes. Accordingly, a focus of this project is to ensure public domain availability of digital elevation data products acquired by the NASA Airborne Topographic Mapper (ATM) and the EAARL systems.

In total, these new coastal remote-sensing, mapping, and point-monitoring tools constitute a unique integrated package of instrumentation and software that may be deployed in support of appropriately timed and scaled zoning decisions by management authorities in order to conserve and sensibly exploit nearshore coastal and marine ecosystems.

Objectives

The project objectives are to:

1. Advance remote-sensing technology for coastal science and management by developing new methods and capabilities for airborne lidar topographic data acquired by the EAARL system
2. Utilize recently developed remote-sensing technology within the USGS CMGP in response to coastal impacts in order to assess, document, and evaluate the condition of affected resources
3. Work collaboratively with the National Park Service to generate, analyze, and publish map products for lidar topographic data acquired by the EAARL, ATM, and other lidar systems
4. Generate and publish map products for coastal topographic data acquired by the EAARL and ATM systems in support of the CMGP projects.