Robust approach to directly measuring water-leaving radiance in the field

It has been a long-standing goal to precisely measure water-leaving radiance (L-w, or its equivalent property, remote-sensing reflectance) in the field, but reaching this goal is quite a challenge. This is because conventional approaches do not provide a direct measurement of L-w, but rather measure various related components and subsequently derive this core property from these components. Due to many uncontrollable factors in the measurement procedure and imprecise post-measurement processing routines, the resulting L-w is inherently associated with various levels of uncertainties. Here we present a methodology called the skylight-blocked approach (SBA) to measure L-w directly in the field, along with results obtained recently in the Laurentian Great Lakes. These results indicate that SBA can measure L-w in high precision. In particular, there is no limitation of water types for the deployment of SBA, and the requirement of post-measurement processing is minimum; thus high-quality L-w for a wide range of aquatic environments can be acquired. (C) 2013 Optical Society of America