Technical note Field reflectance calibration with grey standard reflectors

Abstract

Spectral reflectances of natural targets are measured in comparison with white standards, even when target reflectances are substantially different from those of the white standards. With some targets, the differences are sufficient to require a change in radiometer gain settings. Under these circumstances, measurement errors could likely be reduced if calibration were with standards whose reflectances were closer to those of the targets. This paper describes field testing that compared a black and a grey standard with a white barium sulphate standard. Variations in the reflectance properties of the black and grey standards, although higher than variations in the white standard, were less than 6 percent. The availability and use of such standards would simplify and increase the accuracy of field measurements.