Pre-processing of dual-view FIGOS Data: towards operational BRDF retrieval

Abstract

The Bidirectional Reflectance Distribution Function (BRDF) is an inherent property of natural and manmade materials. Its effects depend on the illumination/observation geometry and wavelengths and are apparent in groundbased, airborne and spaceborne imagery. The BRDF is a fundamental quantity from which all other illumination/reflection configurations can be derived. Calibration and validation of hyperspectral images requires knowledge of the BRDF if spectrodirectional effects are to be accounted for. The BRDF can be retrieved from dual-view field goniometer system (FIGOS) data, which is stored in the spectral database SPECCHIO. The retrieval must be precluded by pre-processing steps, which apply transformations on the raw field data and according metadata. SPECCHIO has been updated to support such pre-processing. Intercalibrations of the involved instruments and temporal corrections lead to a network of operations to be applied to the input data. A generalisation of the processing has led to the concept of the Space Processing Chain, allowing the flexible combination of modules to form complex processing flows as required by the goniometer data pre-processing. The newly added support of intercalibration factors in the SPECCHIO data model will be an important asset in future round robin experiments. The Space Chain approach will operationalise the retrieval of BRDF from dual-view FIGOS data and generally increase the usefulness of the SPECCHIO system by the introduction of user configurable processing.