INITIAL RESULTS FROM A TEST OF THE NASA EXPERIMENTAL ADVANCED AIRBORNE RESEARCH LIDAR (EAARL) FOR THE STUDY OF CORAL REEF ECOSYSTEMS

摘要

Synoptic maps of coral communities based on satellite images generally portray only coarse geomorphological zones and generally are not sufficiently detailed or accurate to be of high value to biologists. Aircraft-based hyperspectral sensors can acquire finer scale images, but are typically quite expensive. Further, water-column contamination of the light reflected from reef benthic classes typically diminish the accuracy of thematic maps derived from aircraft or satellite scanning. The NASA Experimental Advanced Airborne Research Lidar (EAARL) is intended to mitigate these difficulties by combining a hyperspectral scanner with a laser bathymetric sounder on a low cost aircraft. Geopositioning of the Cessna 310 aircraft used for initial flight tests was achieved by the use of an array of GPS antennas that provide both the aircraft flight trajectory (longitude, latitude, altitude) and attitude (pitch, roll, heading). The NASA EAARL instrument package also includes a downlooking digital camera that acquires digital images at a rate of one per second, or roughly every 50 meters along track, during flight operations. Initial flights based at Marathon, Florida were conducted over the Florida Keys reef tract from Dry Tortugas National Park (DTNP ) to Biscayne National Park (BNP). Data was continuously acquired over numerous known reefs in transit to two regions that were swath-mapped, 1) the coral community in central BNP, and 2) an area undergoing rapid channel sedimentation in DTNP. The GPS, flight navigation, and camera and lidar systems performed within design specifications, and lidar reflections were observed from water depths greater than 15 meters.