Total Propagated Uncertainty Modeling for Topobathymetric LiDAR
NOAA’s National Geodetic Survey (NGS) and partner agencies and firms routinely collect topobathymetric lidar data used in NGS’s Coastal Mapping Program. New topobathymetric lidar systems featuring narrow receiver fields of view (FOVs), short pulse widths, low transmit pulse power, and high pulse repetition rates are proving advantageous for collecting dense, seamless data across the land-water interface and in the shallow nearshore zone. While one of the primary uses of the data is updating the National Shoreline depicted on NOAA nautical charts, the bathymetric lidar returns have the potential to also be used for updating chart depths and filling the nearshore hydrographic data void that often exists shoreward of approximately the four-meter depth contour. However, for the bathymetric lidar returns to be integrated into NOAA’s hydrographic surveying and charting workflows, total propagated uncertainty (TPU) models are needed to generate uncertainties in accordance with International Hydrographic Organization (IHO) standards. In a project led by researchers at NOAA NGS, Oregon State University, and the University of New Hampshire, Center for Coastal and Ocean Mapping – Joint Hydrographic Center, new TPU models are being developed to address this need. The initial phase of the project is focusing on TPU modeling for the Riegl VQ-880-G. The general approach involves combining analytical uncertainty propagation with Monte Carlo ray tracing to model uncertainties in the subaerial (in-air) and subaqueous (in-water) portions of the bathymetric lidar measurement process. We will present the first version of the full TPU model and preliminary results from a Gullivan Bay, Florida project site and discuss the planned next steps in producing an operational version of the TPU tool for routine use in NGS’s Coastal Mapping Program.