ISSN 2070-7401 (Print), ISSN 2411-0280 (Online)
Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa


Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2023, Vol. 20, No. 2, pp. 216-225

Retrieval of wind ripple speed from stereo imagery of sea surface

N.A. Bogatov 1 , I.A. Kapustin 1 , A.A. Molkov 1 , A.V. Ermoshkin 1 
1 Institute of Applied Physics RAS, Nizhny Novgorod, Russia
Accepted: 12.04.2023
DOI: 10.21046/2070-7401-2023-20-2-216-225
Stereo imagery of the sea surface is one of the most effective tools for remote sensing wind waves with lengths of half a meter or more. In this paper, we propose a new method for using a series of stereo images to reconstruct the wind ripple velocity field on a long surface wave profile. The presented method is based on detecting characteristic structures on the sea surface (short wind waves, breaking waves, foam, etc.), determining their displacement between two adjacent frames (similarly to the Particle Imaging Velocimetry — PIV method), and recalculating estimated displacement from frame coordinates into three-dimensional Earth coordinates through projection onto a long wave profile obtained using stereo pairs. The test results on the data of stereo imagery of the sea surface carried out from a stationary oceanographic platform in the Black Sea in 2021 are presented in this paper too. The results obtained with the help of the method are in good agreement with the existing ideas about wind waves, as well as with the results of contact measurements. The angular dependence of the wind ripple spectrum and the spatial spectrum of wind waves in a wide range of wave numbers have been experimentally obtained. The results of calculating the wind ripple velocity demonstrated high values of the correlation coefficient with the elevation of the sea surface, which indicates the modulation of the velocity of short waves by the orbital velocities of long waves. The errors of the method and prospects for further development are evaluated.
Keywords: remote sensing, sea roughness, wind waves, stereo imagery, Bragg waves, Doppler shift
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