The KaRIn interferometric altimeter, which is the main instrument of the SWOT mission has been designed to map the topography of water surfaces. While its operating principle is similar to that of previous SAR interferometers such as SRTM or TanDEM-X, its characteristics have been adapted to its purpose: near-nadir incidence to get a strong signal on water surfaces at the expense of land surfaces, small baseline, and Ka-Band wavelength. Despite this, SWOT images show a good coherence on certain types of land surfaces such as sand dunes and early results of topographic processing of SWOT data on these surfaces are very promising. For instance, this could enable new ways to monitor dune migration through SWOT’s high temporal revisit and vertical accuracy.

SWOT is an innovative altimetry mission launched by NASA and CNES in December 2022. The data acquired by the HR mode of the principal instrument KaRIn enable precise estimation of elevation, area and related parameters for continental water surfaces, globally and repeatedly. In this article we briefly present the different science data products, with real-world examples and some preliminary results on performance. The final presentation will report on the global performance assessments which are due for the SWOT Science Validation Meeting in June 2024.

Water detection is a key step in the operational processing of KaRIn HR images from the SWOT mission, which provides water surface extent and elevation for continental water surfaces globally and repeatedly. A new water detection method has been developed for this sensor due to its specific characteristics. In this article we present examples of detected water masks and preliminary assessments of their accuracy. We also provide perspectives for further improvements in the water detection algorithm.

River floodplains and intertidal coastal environments are key areas for which the Surface Water and Ocean Topography (SWOT) altimetry mission is expected to provide valuable data, improving our ability to monitor these dynamic systems. SWOT provides water surface extent and elevation for continental water surfaces globally and regularly. This article presents two methods to derive the topography of such environments from SWOT data. The first one, the waterline method, is the approach currently developed to produce worldwide floodplain/intertidal DEM. The second method uses a direct approach by exploiting InSAR heights extracted directly from SWOT products. An example is shown for the Bay of Veys located in Normandy (France).

The aim of this study is to investigate the performance of SWOT in generating intertidal Digital Elevation Models (DEMs) using the waterline method. To this end, tests were made by generating intertidal DEMs from SWOT-type observables for two intertidal bays situated on the French coast: the Arcachon Bay and the Bay of Veys. SWOT-type observables were simulated using the SWOT Hydrology Toolbox developed by the French space agency (Centre National d'Études Spatiales (CNES)). By comparing SWOT-derived DEMs to the validation DEMs, SWOT showed a great potential for monitoring intertidal topographies. Mean Absolute Errors (MAEs) and Root Mean Square Errors (RMSEs) reached respectively 5.2 cm and 8.4 cm for the Arcachon Bay and 10.2 cm and 17.3 cm for the Bay of Veys. However, the accuracy of SWOT-derived DEMs is dependent on SWOT's orbit.

The goal of the Surface Water and Ocean Topography (SWOT) mission, a future wide-swath radar altimeter, is to measure the elevations of ocean and continental water surfaces with unprecedented precision. A simulator of SWOT high-rate (HR) interferometric SAR images has been developed to provide SWOT-like data to scientists and as a tool to develop and test HR ground processing algorithms. In this letter, we evaluate the errors of the extracted water levels in different hydrodynamic and topographic contexts in the Seine estuary based on simulated SWOT HR data. The results confirm height errors generally below 10 cm after km-scale averaging for the majority of the observations. Higher errors mostly occur in areas where the surrounding topography causes layover. This letter also reveals the interactions between tide and streamflow and their impact on the spatial variability of the water levels in the estuary.

The upcoming Surface Water and Ocean Topography (SWOT) mission, projected for launch in 2021, will provide global measurements of water elevation for ocean and continental water bodies with unprecedented resolution and accuracy. This article describes how the variations in height and extent of continental water surfaces, as measured by SWOT's principal instrument, the Ka-band Radar Interferometer (KaRIn), can be used to derive floodplain Digital Elevation Models (DEMs), in principle with submeter accuracy. The proposed method is based on InSAR processing, refined geolocation, and the so-called bath-tub ring approach. Preliminary results obtained on multitemporal simulated SWOT data are presented.

Surface Water and Ocean Topography (SWOT) is a future wide-swath radar altimetry mission. The main instrument is the Ka-band radar interferometer (KaRIn). It provides interferometric radar images that will be processed to obtain water elevation estimates worldwide. Due to the specific geometric and radiometric characteristics of KaRIn/SWOT, the phase-to-height conversion is one of the most critical processing steps. We propose methods to estimate water heights without using classical approaches based on spatial phase unwrapping and control points. Results obtained on the simulated SWOT data are shown.

This article summarizes the data processing of the proposed wide-swath altimetry mission Surface Water and Ocean Topography (SWOT), and more specifically the processing steps up to level 2 for the Ka-band Radar Interferometer (KaRIn), which is a near-nadir viewing bistatic SAR system. A general overview of the proposed processing chains and data products is given, and some particularly challenging processing steps are commented on.