Time-resolved polarimetry over water waves: relating glints and surface statistics

Abstract

The phenomenon of sunglint, well known in satellite remote sensing, lacks a fundamental characterization under controlled laboratory conditions. Exploiting an apparatus specifically assembled for the purpose, we examine the signal collected by a photopolarimeter, pointed at a wavy water surface with measurable statistics and illuminated by a laser source. We also analyze the wave slope distributions, retrieved with an imaging system, and correlate them with the time series of glints. More particularly, we investigate the link between the occurrence of glints and that of the slopes from which they originate. In this context, the results obtained by applying the Hilbert-Huang transform technique to the slope time series are compared with those obtained through a traditional Fourier transform. This novel study first identifies the individual atomic glints as Fresnel reflection originating from a single wave facet. It then discusses the periodic character of a sequence of glints generated by a gravity wave state, as opposed to the erratic behavior of glints typical of capillary wave states. In mixed gravity-capillary conditions, it is shown that the glint properties are governed mainly by the capillary regime.

Sunglint Detection for Unmanned and Automated Platforms

“…It was therefore assumed that for the available measurements sunglint and whitecaps/foam led to contaminated measurements. It is for this reason that in future studies the contribution of whitecaps and foam be specifically investigated with respect to sunglint flagging, possibly utilising novel glint measurement apparatus e.g., [31,32] integrated with sunglint and wave models such as [4,5,7,15,33]. …”

Characterization of Sun Glitter Statistics in Ocean Video

“…A number of controlled experiments have been performed in wind-wave tanks under various set-ups, including those described in [66][67][68][69][70][71][72][73][74][75][76][77].…”

Performance of eliminating sun glints reflected off wave surface by polarization filtering under influence of waves

“…Gál et al measured the reflection polarization pattern of the flat water surface under a clear sky firstly [7]. But under actual conditions, most of sea surfaces are not flat and calm but rough and waving [1,8]. Cox and Munk provided an analytical formula expressed by probability distribution of micro facets' slope to represent the relation between surface roughness and wind speed [9,10].…”

“…Cox and Munk provided an analytical formula expressed by probability distribution of micro facets' slope to represent the relation between surface roughness and wind speed [9,10]. The changing of micro facets' slope causes the polarization properties of glints varying all the time [8]. Zhou et al simulated the polarization patterns of skylight reflected off wave water surface in different conditions such as solar zenith angle, wind speed, wind direction and so on.…”