On the brightness threshold dependence of nonlinear wave spectrum estimation from sunglint

The retrieval of ocean wave spectra from sunglint patterns holds considerable promise as a remote sensing technology which could potentially be implemented on a variety of platforms using cheap, compact, commercial off-the-shelf equipment. Following the development of an inversion technique which assumed linear hydrodynamics of the sea surface, a new, generalised approach has been formulated to incorporate nonlinear effects which are pervasive in the real ocean environment. In each method, the starting point for the retrieval is the calculation of the relevant cumulant functions of the binary glint pattern, as defined by means of a brightness thresholding operation on the raw sunglint image. Here we consider the effects of the choice of threshold value, and whether an objective set of criteria exist for its selection.