Measuring water surface elevation and slope with airborne ka-band insar: airswot in the delta-x campaign

AirSWOT is an airborne Ka-band synthetic aperture radar, capable of mapping water surface elevation (WSE) and water surface slope (WSS) using single-pass interferometry. AirSWOT participated in the NASA EVS-3 Delta-X campaign in 2021, which combined remote sensing from multiple instruments with an extensive coincident field data collection in the Mississippi River Delta, Louisiana, USA. As part of Delta-X, AirSWOT flew a greater number of flight lines than in previous AirSWOT campaigns, collecting a significant volume of data which can provide insight into the dynamics and quantity of water in the Atchafalaya and Terrebonne basins of the Mississippi River Delta. AirSWOT data has been processed into publicly available data products at a number of processing levels, depending on user needs and application, including a new Level-3 water surface product developed specifically for Delta-X. The Level-3 water surface product uses water masking and spatial averaging to produce a science-ready point data product, using the Level-2 GeoTIFF raster products as input. The Level-3 data allows profiles of WSE and WSS within designated channels to be easily calculated. AirSWOT estimates of WSE from Delta-X have been compared to in situ water level data with root mean square error (RMSE) of 9 cm, excluding data from two flights in September, 2021 which were adversely affected by poor weather conditions that affected the instrument hardware. Including all data, the RMSE increases to 12 cm. We have also used AirSWOT to help estimate the vertical datum for water level gauges without accurate vertical reference information. AirSWOT is capable of mapping WSE and WSS at high resolution in spatially complex coastal environments, making it a valuable instrument for studying these regions.