BRDF and illumination calibration for very high resolution imaging sensors

The advent of very high resolution airborne and spaceborne imaging systems provides opportunities for quantitative mapping and monitoring applications using data from such sensors. Radiometric calibration is an essential step for carrying out quantitative analysis. In this paper, a radiometric calibration approach for high resolution image data is presented, which includes Bi-directional Reflectance Distribution Function (BRDF) calibration, terrain illumination correction for removal of illumination effects caused by undulating surfaces, and detection of shadow and occlusion using high resolution Digital Surface Models (DSM). These methods are showcased in an urban environment monitoring project named Urban Monitor. This project employs photogrammetric sensors to acquire high resolution panchromatic and multi-spectral data. Some radiometric calibration results from the Urban Monitor project are presented. Particular issues such as several shadows cast by above ground objects are addressed and possible solutions are explored. Future work inspired by the recent advances from scene perception research is discussed.