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A Laboratory Goniometer System for Measuring Reflectance and Emittance Anisotropy
Laboratory of Geo-Information Science and Remote Sensing, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands
Remote Sensing Laboratories, Department of Geography, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
Wageningen UR Greenhouse Horticulture, P.O. Box 644, 6700 AP Wageningen, The Netherlands
Alterra, Wageningen University & Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands
* Author to whom correspondence should be addressed.
Received: 19 September 2012; in revised form: 7 December 2012 / Accepted: 11 December 2012 / Published: 13 December 2012
Abstract: In this paper, a laboratory goniometer system for performing multi-angular measurements under controlled illumination conditions is described. 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. This paper also presents three showcases of these different measurement set-ups in order to illustrate its possibilities. Finally, suggestions for applying this instrument and for future research directions are given, including linking the measured reflectance anisotropy with physically-based anisotropy models on the one hand and combining them with field goniometry measurements for joint analysis with remote sensing data on the other hand. The speed and flexibility of the system offer a large added value to the existing pool of laboratory goniometers.
Keywords: reflectance anisotropy; BRDF; emittance anisotropy; laboratory goniometer; biophysical parameter retrieval
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Roosjen, P.P.J.; Clevers, J.G.P.W.; Bartholomeus, H.M.; Schaepman, M.E.; Schaepman-Strub, G.; Jalink, H.; van der Schoor, R.; de Jong, A. A Laboratory Goniometer System for Measuring Reflectance and Emittance Anisotropy. Sensors 2012, 12, 17358-17371.
Roosjen PPJ, Clevers JGPW, Bartholomeus HM, Schaepman ME, Schaepman-Strub G, Jalink H, van der Schoor R, de Jong A. A Laboratory Goniometer System for Measuring Reflectance and Emittance Anisotropy. Sensors. 2012; 12(12):17358-17371.
Roosjen, Peter P.J.; Clevers, Jan G.P.W.; Bartholomeus, Harm M.; Schaepman, Michael E.; Schaepman-Strub, Gabriela; Jalink, Henk; van der Schoor, Rob; de Jong, Arjan. 2012. "A Laboratory Goniometer System for Measuring Reflectance and Emittance Anisotropy." Sensors 12, no. 12: 17358-17371.