The Visibility of rms Slope Variations on the sea Surface
A model relating viewing geometry, sky conditions, and statistical sea surface parameters is presented. The model is used to estimate the relative visibility of surface perturbations manifested by a variation in the rms surface slope. These estimates are presented for a variety of geometries in the solar plane assuming a clear sky and two different wind speeds (~ 2 and 7 m/s). The results of this analysis, applicable to a unidirectional radiometer with no temporal averaging, show the visibility of surface perturbations to be maximized by geometries with large gradients in the slope-to-luminance transfer function (within the glitter pattern or near the horizon). Detectability of these perturbations, as measured by the luminance SNR sensitivity to rms surface slope variations, is maximized by either large gradients, as for the visibility, or very small gradients in the slope-to-luminance transfer functions (90° away from the glitter pattern). It is shown that improvements in the estimated detectability can be obtained through spatial and temporal averaging. Two methods for quantitatively estimating these improvements are presented.
KeywordsTransfer Function Internal Wave Contrast Sensitivity Wind Wave Solar Zenith Angle
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