Satellite SAR Bathymetry


The SAR-bathymetry application is based on the detection of the swell wave’s pattern in Synthetic Aperture Radar (SAR) satellite images. Input SAR images from Sentinel-1 (S1), KompSAT-5 (K5), TerraSAR-X (TSX), RadarSAT, Cosmo-SkyMed, EnviSAT or other High-Resolution SAR images, are collected from the Co-ReSyf catalogue, providing quicklooks to facilitate user selection of relevant images and the general region/coast of application. The images should show a pattern of nearly regularly-spaced wave crests and troughs (respectively, lighter and darker grey-scales) that, through adequate processing steps, allow to calculate the corresponding principal ocean wavelength and wave direction.
For each SAR image, a pre-check image adequacy is verified, based on additional information from wind field data (able to produce the Bragg scattering, which, together with the hydrodynamic and tilt modulations are the physical mechanisms through which a SAR image shows wave crests and troughs), and wave climate data (to identify swell conditions).

The user should select his/her Region Of Interest (ROI) within the SAR image, taking into consideration that the possible and likely region of application is confined to the continental shelf, bounded at the coast by the wave breaking region (at depths of the order of 1 to 10 m) and at the sea by the continental shelf break or the wave deepwater limit (where the depth is equal or greater than one half of the wavelength).
Within the ROI, the operator must further choose the resolution of the bathymetric grid, where the depth is then estimated at each grid-point from the knowledge of the dominant wavelength at the sub-image (with an algorithm/user selected length) centered at that point, and the swell-wave period retrieved from ancillary data or the image-estimated deep-water wavelength. The method relies on the inversion of the wave number dispersion relationship.

The output of the algorithm consists in a Digital Elevation Model (DEM) for the target area, and/or a geo-referenced map with bathymetric contours computed from the DEM.

If you plan to use this application and have some doubts or want to share your problems or your results using it, you can write a comment on this topic, and ask for some feedback from the Co-ReSyF community.