Estimation of Shallow Water Bathymetry Using Linear Wave Dispersion Theory on a Single Resourcesat-2 LISS-IV Image Near Indian East Coast

The current study explores the applicability of a method based on image correlation to retrieve shallow water bathymetry from a single Resourcesat-2 LISS-IV satellite imagery. The method exploits the time lag between the scanning in different bands of LISS-IV in a single data acquisition using image correlation. The Linear Wave Dispersion Theory relates wavelength (λ) and wave celerity (c) of nearshore sea waves to depth (h) of water. Wherever depth of water is less than half of wavelength, then wavelength and wave celerity decreases as a result of decrease in depth when waves approach the coast. A horizontal grid is defined over the satellite imagery and resolution cells are taken with each grid point as the center of a cell. Dominant wavelengths are extracted for each cell over the water region, using Fast Fourier Transform (FFT) spectrum and corresponding wave celerity is computed using the pixel offset in wave’s direction of motion between two bands. Each λ-c pair in a cell is substituted in the linear wave dispersion relation and corresponding depth is calculated. Finally, a weighted average of the calculated depths is taken as bathymetry at the grid point. The resulting bathymetry map closely follows the trend as per GEBCO_2020 bathymetry grid.