22 December 1992 Determination of sea topography and its effect upon restoration of imagery acquired by viewing through the sea surface
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Abstract
Imagery acquired by viewing through the air-sea interface is generally degraded by refraction at the interface, as well as by atmospheric and in-water scattering. A key problem in the restoration of such imagery is the removal of interfacial refractive effects. We have previously shown the feasibility of image restoration via model-based compensation for interfacial refraction and volume scattering distortions. Our techniques are contingent upon the accurate determination of sea topography, which we propose to accomplish via pointwise optical time- domain reflectometry (OTDR). Recently, consideration has been given to interfacial sensing methods such as glint imaging and stereophotogrammetry, which can be implemented with passive sensors but exhibit deficiencies which limit their utility in sensing sea topography. In this paper, we analyze salient errors inherent in the foregoing techniques, and briefly discuss errors incurred by sonic and microwave echolocation. We show that OTDR-based sensing is superior to stereophotogrammetry, whose accuracy, range, and field of view is resolution- limited. Additionally, we analyze and demonstrate the effect of topographic sensor errors upon feature localization in the reconstructed target imagery. Given a simulated wave height of 1.5 meters, 100 m sensor altitude, and 5 m target depth, we show that our image restoration model is stable, and remains useful, when the estimate of sea surface elevation is corrupted by a ranging error of up to 25.5 cm (peak-to-peak) at an error cross-section of 25 percent or less.
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Mark S. Schmalz, Mark S. Schmalz, "Determination of sea topography and its effect upon restoration of imagery acquired by viewing through the sea surface", Proc. SPIE 1749, Optics of the Air-Sea Interface: Theory and Measurement, (22 December 1992); doi: 10.1117/12.138861; https://doi.org/10.1117/12.138861
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