Measurement and modeling of the spectral and directional reflection properties of lichen and moss canopies

Both spectral and directional reflection characteristics of terrestrial surfaces are of interest for remote sensing applications. We report on detailed laboratory measurements of the Cladina stellaris and Flavocetraria nivalis lichens and the Racomitrium lanuginosum moss canopies carried out at the European Goniometer facility at the Joint Research Center, Ispra, Italy, we present bidirectional reflectance factor data in the blue, green, red, and near-infrared parts of the spectrum. The moss had enhanced backscatter in the visible spectrum and was strongly backscattering in the near-infrared. We successfully fitted the low-dimensional parametric model of Rahman, Pinty, and Verstraete to our experimentally determined bidirectional reflectance factors. By means of cross-validation, we assessed the number of randomly sampled data points necessary to guarantee reliable model inversions. We found that approximately 100 measurement points were needed for our experimental data. Finally, we applied bootstrap techniques to show that the root-mean-square modeling error was as low as 5.7% for our chosen targets and model. Our findings, combined with digital elevation models and atmospheric radiative transfer models, may result in enhanced detection of lichens from optical satellite data. The complete dataset is available from the first author. (C)Elsevier Science Inc., 2000.