Active-Passive Spaceborne Data Fusion for Mapping Nearshore Bathymetry

"In anticipation of the National Aeronautics and Space Administration (NASA) ICESat-2 mission, which will employ the Advanced Topographic Laser Altimeter System (ATLAS), a 532 nm photon-counting Light Detection and Ranging (lidar), we demonstrate a spaceborne data-fusion approach that has the potential to significantly shrink the global nearshore data gap often referred to as the "white ribbon". Bathymetry algorithms relying on multispectral imagery are conventionally limited by the availability of in situ reference depths, particularly in remote or difficult-to-map areas. Therefore, a completely spaceborne approach could greatly extend the usefulness of such algorithms. The approach is tested with data from NASA's airborne ICESat-2 ATLAS simulator, Multiple Altimeter Beam Experimental Lidar (MABEL), and passive optical imagery from Landsat-8 using an existing spectral-ratio algorithm. The output bathymetric data set agrees with high-resolution Fugro LADS MK II bathymetric data to within an RMS difference of 1.1 m. The spatiotemporal variability of areas where this spaceborne data-fusion approach will potentially be useful is evaluated, based on worldwide coastal water clarity as interpreted from Visible Infrared Imaging Radiometer Suite (VIIRS) Kd(490) data.