Inflight Intersensor Radiometric Calibration Using the Reflectance-based Method for Landsat-type Sensors

Improvements in the protocols and approaches used for the inflight radiometric calibration and validation of imaging sensors using the reflectance-based method has led to the feasibility of this method for the intercomparison of multiple sensors. The philosophy presented here is different than the typical cross-calibration techniques used successfully since the 1980s in that it does not require near simultaneous views of the ground. The concept is similar to the use of spherical integrating sources as a calibration standard in multiple laboratories for multiple sensors. The maintenance of traceability of these sources to a set of specified standards allows sensors calibrated in the same way to agree within the uncertainties of the methods. Extending the idea of a calibration source to that of a ground-reference target readily shows how these concepts can be used inflight. Results using ASTER, Landsat-5 TM, Landsat-7 ETM+, and ALI illustrates that the method can be applied with precision approaching 1% (one standard deviation) in many spectral bands. The method relies on selecting data sets based on specific atmospheric and surface conditions and scaling data sets based on band-to-band correlations. Results are not limited to a single site and results from one sensor can be compared to those of another sensor without the need for coincident acquisitions. Disagreements between sensors in excess of 1.4% would be indicative of possible biases between the sensors.