Determining the Vector of Slopes of the Water Surface from its Image Under Natural Illumination

Turlaev D. G.

Some results of restoration of a vector of slopes of the wavy water surface on its image received under the conditions of a natural lighting at a clear sky are presented. For the experiment an inflatable pool with a diameter of ~ 2 m was used. For the attenuation of the backscattered signal the water is saturated with nigrosine. Images were recorded on a digital photocamera. The waves were created by hand. Except the image of the wavy water surface the photo of the area of the sky, reflected in calm water participates. Distribution of brightness of the sky reflected in quiet water within a photoshot is considered to be a linear. Under the above conditions, a component of the slope vector, collinear to the brightness gradient of the sky, was found. For its finding it was used the image of the wavy water surface and a photo of the same site of water in the absence of waves. The second component was determined directly from the found one, using the fact that both components of the slope vector are derivatives of one scalar function — the function of the water surface elevations. The algorithm used made it possible to find the slopes of waves running in different directions with acceptable accuracy, except for those that propagated near the normal to the sky brightness gradient.

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