Abstract

The spectral radiance of breaking wind waves on an ocean or lake, commonly referred to as whitecaps, has been measured using a multi-spectral scanner mounted in an aircraft. At least seven optical windows extending from .57 to 1.64 μm were employed. The texture of the scene varies with the interrogating wavelength. Many narrow streaks become apparent in the near visible band at 1.64 μm than in the visible bands. Apart from a factor of at least 10 in radiance between the whitecaps and the background water, the breaking waves demonstrate a different spectral distribution. In addition, a change in sensitivity occurs in the spectral radiance of the whitecaps at a wavelength of about .8 μm in the oceanic cases and .65 μm in the fresh water cases which is not observed in the light from the background water. Areas identified as foam indicate a behaviour intermediate in intensity and spectral distribution between whitecaps and background. Several attempts to automatically categorize pixels according to their spectral, probabilistic and spatial characteristics will be described.

© 1986 Optical Society of America