A major research item for the coming years is assessing the anisotropic reflectance behaviour of vegetation and soils, as described by the bidirectional reflectance distribution function (BRDF). Information on the BRDF of targets is relevant for normalizing images taken under different illumination and/or viewing conditions, but on the other hand multi-angular observations also provide additional information that can be used to improve the accuracy of retrieved products. To support on-going research in this field, we realized a laboratory measurement facility to assess the anisotropic reflectance behaviour of soils, leaves and small canopies under controlled illumination conditions.
A commercially available robotic arm enables the acquisition of a large number of measurements over the full hemisphere within a short time span making it much faster than other goniometers. In addition, the presented set-up enables assessment of anisotropic reflectance and emittance behaviour of soils, leaves and small canopies. Mounting a spectrometer enables acquisition of either hemispherical measurements or measurements in the horizontal plane. Mounting a thermal camera allows directional observations of the thermal emittance. A detailed description of the system can be found in Roosjen et al. (2012).
Research within the Laboratory of Geo-Information Science and Remote Sensing is focused on:
Effects of soil moisture content on reflectance anisotropy - Laboratory goniometer measurements and RPV model inversions
Remote Sensing of Environment 170 (2015). - ISSN 0034-4257 - p. 229 - 238.
Investigating BRDF effects based on optical multi-angular laboratory and hyperspectral UAV measurements
In: Fourier Transform Spectroscopy, FTS 2015. - : OSA - The Optical Society
Measuring and modeling the effect of surface moisture on the spectral reflectance of coastal beach sand
PLoS ONE 9 (2014)11. - ISSN 1932-6203 - 9 p.
A laboratory goniometer system for measuring reflectance and emittance anisotropy
Sensors 12 (2012)12. - ISSN 1424-8220 - p. 17358 - 17371.