Abstract

Visibility, a property measured based on human vision, is a common and widely used measurement to represent the quality of air and water. To visibility, theories have been developed in the past century for measurements in both air and water. This includes the century-old Koschmieder model for visibility in air and the Duntley-Preisendorfer model for visibility (Secchi disk depth) in water, as well as recent model by Lee et al. Here we present a general relationship for the Law of Contrast Reduction based on radiative transfer, which is the key to deduce visibility in both media. And from this general relationship, it suggests the Koschmieder model is applicable only to situations when a common-size object can be viewed 10's of kilometers away, while the Duntley-Preisendorfer model is not applicable for a common size Secchi disk when viewed in water. We further highlight the difference in “visibility” between "simple detection" and "clear recognition", a key difference of “visibility” in air and water.

© 2019 IEEE