Abstract
With video equipment and image processing software the authors have measured the whitecap coverage of the sea surface near the Dutch coast. Reality proved the initial idea about the simplicity of this way of whitecap measurement to be overly optimistic. A model was developed that produces a theoretical estimate of the whitecap percentage as a function of the wave age, which in turn depends on the wave peak frequency and the friction velocity in the air. The comparison between the measured whitecap coverage and the model results shows an order of magnitude correspondence for most data. A group of outliers appears to be connected to the strength of the current.