Early Results of Simultaneous Terrain and Shallow Water Bathymetry Mapping Using a Single-Wavelength Airborne LiDAR Sensor

In this paper we present results obtained with a new single-wavelength LiDAR sensor which allows seamless sub-meter mapping of topography and very shallow bathymetry in a single pass. The National Science Foundation supported National Center for Airborne Laser Mapping (NCALM) developed the conceptual design for the sensor that was built by Optech Inc. The new sensor operates at a wavelength of 532 nm and is fully interchangeable with an existing 1064 nm terrain mapping sensor operated by NCALM, connecting to the same electronics rack and fitting into the same aircraft mounting assembly. The sensor operates at laser pulse repetition frequencies (PRFs) of 33, 50 and 70 kHz, making it possible to seamlessly map shallow water lakes, streams, and coastal waters along with the contiguous terrain, including rural and urban areas. This new sensor has been tested in a wide variety of conditions including coastal, estuarine and fresh water bodies, with water depths ranging from 20 centimeters to 16 meters, with varying benthic reflectivity and water clarity. Observed point densities range from 1-4 points/m(2) for terrestrial surfaces and 0.3-3 points/m(2) for sub water surfaces in a single pass, and double these values when the data are collected with 50% side swath overlap, a minimum standard for NCALM's airborne LiDAR surveys. The seamless high resolution data sets produced by this sensor open new possibilities for geoscientists in fields such as hydrology, geomorphology, geodynamics and ecology.