Evaluating SWOT's interferometric capabilities for mapping intertidal topography

The Surface Water and Ocean Topography (SWOT) mission, originally designed for observing ocean and inland water bodies, can be a valuable tool for mapping the topography of intertidal flats. This study provides the first demonstration of SWOT's ability to measure intertidal topography using simultaneous interferometric acquisitions. Observations acquired between April and July 2023, during the calibration/validation (CALVAL) phase of the mission, were used. SWOT-derived intertidal Digital Elevation Models (DEMs) were generated from level-2 High-Rate Pixel Cloud (L2_HR_PIXC) products and compared to airborne and UAV LiDAR-derived DEMs. Our results indicate a high reliability of the SWOT observations with a mean absolute error lower than 0.49 m, reaching 0.13 m in specific areas. This validation confirms SWOT's contribution for coastal studies beyond water level mapping, showcasing its broader applicability in the monitoring and management of coastal and estuarine environments. • SWOT can effectively map intertidal topography, expanding the mission scientific applications. • SWOT enables intertidal mapping thanks to the strong backscattering in these regions. • SWOT-derived intertidal topography matches LiDAR benchmarks (airborne and UAV). • Root Mean Squared Errors were below 20 cm over the UAV-covered strip. • SWOT provides accurate topography from single acquisitions at low tide.