Intercomparison of Imaging Sensors using Automated Ground Measurements

The reflectance-based method is a vicarious approach providing absolute radiometric calibration. A desire to increase the number of possible reflectance-based calibrations led the University of Arizona Remote Sensing Group (RSG) to deploy multispectral, downlooking radiometers at the RSG´s Railroad Valley test site in Nevada. The radiometers are coupled with data from a sun photometer to provide the information needed for reflectance-based calibration without the need for on-site personnel. Results from these radiometers show similar uncertainties as on-site methods, and early results have led to their use with geostationary sensors, for derivation of surface bi-directional reflectance effects, and for comparisons of biases between sensors. The results show that radiometers with a single view angle are sufficient to characterize BRDF effects for Railroad Valley Playa. The results also give confidence in the automated approach as a means for cross-calibration relative to the vicarious results providing similar intercomparison results as with on-site personnel.