An Improved Scheme for Correcting Remote Spectral Surface Reflectance Simultaneously for Terrestrial BRDF and Water‐Surface Sunglint in Coastal Environments

Abstract

AbstractGlobal spectroscopic missions, such as NASA’s Surface Biology and Geology, will observe coastal environments and must account for the optical properties of both land and sea. Specifically, they must consider reflectance effects that arise from interactions between surface structures and variable observing geometries that are unique to terrestrial and aquatic domains. Over vegetated surfaces, Bidirectional Reflectance Distribution Function (BDRF) effects must be corrected to consistently map vegetation properties. At the water surface interface, sunglint effects must be corrected to estimate water column and benthic properties. Current analyses focus on vegetation or aquatic domains and do not easily address environments with mixed water and vegetation cover. Wetland environments within global spectroscopic data sets will pose a challenge to correction methods when scientific applications in coastal regions require continuous reflectance correction over both surface types. Here, we present the first simultaneous treatment of terrestrial BRDF and aquatic sunglint in a wetland environment. We evaluate existing vegetation‐BRDF correction methods and pair them with sunglint correction of aquatic pixels. We test multiple sunglint correction strategies to produce continuous corrected products over both vegetation and water surfaces. We show that the addition of sunglint correction in wetland environments significantly reduces error between overlapping image regions. Comparisons between airborne and in situ data demonstrate sub‐percent error in remote estimates of water‐leaving reflectance. Our results demonstrate the importance of both BRDF and sunglint corrections in wetland environments. A unified treatment will be critical for global‐scale hyperspectral spectroscopy missions.