Retrieval of 2D Wave Spectra from TerraSAR-X Imagery in the Baltic Sea
Rikka, Sander; Uiboupin, Rivo; Alari, Victor; Viitak, Marili
Marine Systems Institute at TUT, ESTONIA
Previous studies have demonstrated beneficial use of SAR imagery for finding significant wave height, wave direction and wave number of ocean swell. The TerraSAR-X data used in current work enables to study small scale spatial variation of surface waves in near shore regions where local bathymetry, surface wind and surface currents have active interaction with gravity waves. Common SW and W winds in the Baltic Sea produce wavelengths up to 130 meters, but mainly 20 to 70 meters long waves are observed. Period of the most frequent waves are between 2 to 7 seconds. As the TerraSAR-X data has high spatial resolution (0.75-1.5 m) compared to other sensors (e.g. ENVISAT/ASAR), it enables to detect the 2D wave spectrum even in the Baltic Sea where the scale of waves is smaller compared to long ocean waves. In the current study 18 TerraSAR-X images were used - 15 in StripMap mode and 3 in SpotLight mode.
Main objective of current study is to develop and implement methods for retrieval of two dimensional (2D) ocean/marine wave spectra (and thus peak wavelength, wave direction, wave number and significant wave height) from TerraSAR-X imagery.
Another aim is to compare results between developed SAR based algorithm, SWAN wave model and in situ measurements to detect the differences. The calibration coefficients of algorithm for retrieval of significant wave height from SAR imagery will be tuned using hindcast results of SWAN wave model and buoy measurements. The results of the comparison are presented in the study.