Diver Visibility Summary

Special Operations and Mine Warfare require the prediction of visibility for divers and cameras using ambient light. We propose here a simple, robust, low power visibility meter that can be deployed from autonomous vehicles, moorings, profilers, or directly by divers. The device is based on a thorough analysis of visibility algorithms. Horizontal contrast reduction is governed by the ambient light beam attenuation coefficient. The device will therefore determine that parameter, i.e. it always determines the attenuation of the light that is used to "see" objects, and therefore presents a true measure of visibility. The same device can also determine the radiance attenuation coefficient in any direction. This parameter is additionally needed when the viewing angle is not horizontal. The meter is thus appropriate for determination of the contrast reduction in any direction under natural lighting conditions. The device will be similar in size to existing single wavelength beam attenuation meters. The proposed device can employ a filter to adjust for the different spectral sensitivities of humans and cameras. By using ratios of radiances, the device will be insensitive to environmental effects on electronics and hence will be extremely stable electronically. Biofouling can be prevented by use of shutters.