Synthetic aperture radar (SAR) images of ship wakes frequently exhibit long streaks. Some of the streaks are attributed to the Kelvin V-wave wake, and others are attributed to the turbulent and bright narrow V-wake. Ocean waves reduce the detectability of Kelvin wakes in SAR images. The SAR imaging of Kelvin wakes of two ships with different dimensions moving in rough sea is studied theoretically. The Kelvin wakes are simulated using the Michell theory. The random sea surface is simulated using the Pierson-Moskowitz type wave spectrum. The elevations of the points of the water surface and their velocities and accelerations are considered as a superposition of a ship's coherent waves and wind waves. A two-scale composite model and the velocity-bunching integral are used to simulate the intensity of SAR images of a disturbed sea surface with an embedded Kelvin wake. The fast discrete Radon transform is applied to detect the boundaries of the simulated Kelvin wakes. The probabilities of missing detections (PMD) and false alarms (PFA) are estimated numerically. The influence of ships, wind, and SAR parameters on PMD and PFA is discussed. It is illustrated that PMD/PFA strongly depend on the sea state. Index Terms-Probability of false alarms (PFA), probability of missing detections (PMD), Radon transform (RT), sea waves, ship wake, synthetic aperture radar (SAR).
The nearshore wave field within Monterey Bay, California, is studied using remote sensing imaging by an interferometric synthetic aperture radar (INSAR) and simultaneous ground‐based measurements. It is shown that INSAR imagery of the ocean surface offers some advantages over conventional synthetic aperture radar. Because of the direct imaging mechanism of INSAR, quantitative information about the complicated wave field can be obtained. The INSAR‐derived directional energy density spectra and the corresponding ground‐based spectra compare well.
Microwave remote sensing of the ocean surface using Synthetic Aperture Radar (SAR) is of great interest due to its high resolution and the potential of nearly instantaneous coverage of large areas. The experience accumulated in ocean imaging by SAR indicates that there are substantial difficulties in interpretation of the obtained images of ocean wave systems. Ocean surface currents are almost impossible to obtain from SAR imagery. The present paper reports on measurements of ocean surface currents based on imaging of the nearshore regions of the Monterey Bay using an interferometric SAR. The method is a modification of the conventional SAR which employs two spatially separated antennas. This modification allows one to construct an interferogram from the two complex images obtained by each antenna, which provides direct mapping of the observed surface velocities. The present results demonstrate the advantages of this novel technique in studying nearshore ocean surface dynamics. In particular, spatial distribution of the longshore current velocity is presented.
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