Normalization of illumination conditions for ground based hyperspectral measurements using dual field of view spectroradiometers and BRDF corrections

BRDF effects present in dual field-of-view spectroscopy datasets were investigated. A data-driven normalization procedure was developed by decomposing the target BRDF into a target specific Lambertian component and a bi-directional component characterizing a group of similar targets,. The normalization method was used to convert reflectance factors obtained under cloud obscured conditions into clear sky conditions. An evaluation on four targets measured under different illumination conditions suggests that the normalization can reduce relative reflectance errors between 400 and 1800 nm from 15% to less than 5% even under full cloud obscuration. At higher wavelengths a decreased signal-to-noise ratio increases the error level.