Furrow microrelief influence on the directional hiperspectral reflectance of soil at various illumination and observation conditions

The paper describes the results of an experiment designed to investigate the affects of furrow microrelief on the soil hyperspectral directional reflectance spectra collected at various illumination and observation conditions. The reflectance of four soil surfaces formed of the same sandy material, the smooth and the others with furrows of different depth, were measured by a laboratory prototype goniometric spectral device. The most spectacular effects of the furrows on the hyperspectral BRF spectra of the surfaces were observed along the light source principal plane from forward directions to the source at possible high view zenith angles if the source zenith angle θs is extremely high and its beams reaches the furrows at the horizontal angle of 90°. It was also found that the absorption features of the soil material used in the experiment, located at around 1420 nm, become less visible with increasing of the θs, independently on shape of the surfaces.