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The Improved Dual-view Field Goniometer System FIGOS
University of Zurich, Remote Sensing Laboratories, Winterthurerstrasse 190, 8057 Zurich, Switzerland
* Author to whom correspondence should be addressed.
Received: 3 July 2008; in revised form: 22 August 2008 / Accepted: 24 August 2008 / Published: 28 August 2008
Abstract: In spectrodirectional Remote Sensing (RS) the Earth’s surface reflectance characteristics are studied by means of their angular dimensions. Almost all natural surfaces exhibit an individual anisotropic reflectance behaviour due to the contrast between the optical properties of surface elements and background and the geometric surface properties of the observed scene. The underlying concept, which describes the reflectance characteristic of a specific surface area, is called the bidirectional reflectance distribution function (BRDF). BRDF knowledge is essential for both correction of directional effects in RS data and quantitative retrieval of surface parameters. Ground-based spectrodirectional measurements are usually performed with goniometer systems. An accurate retrieval of the bidirectional reflectance factors (BRF) from field goniometer measurements requires hyperspectral knowledge of the angular distribution of the reflected and the incident radiation. However, prior to the study at hand, no operational goniometer system was able to fulfill this requirement. This study presents the first dual-view field goniometer system, which is able to simultaneously collect both the reflected and the incident radiation at high angular and spectral resolution and, thus, providing the necessary spectrodirectional datasets to accurately retrieve the surface specific BRF. Furthermore, the angular distribution of the incoming diffuse radiation is characterized for various atmospheric conditions and the BRF retrieval is performed for an artificial target and compared to laboratory spectrodirectional measurement results obtained with the same goniometer system. Suggestions for further improving goniometer systems are given and the need for intercalibration of various goniometers as well as for standardizing spectrodirectional measurements is expressed.
Keywords: Dual-view field goniometer system FIGOS; BRF retrieval; BRDF; atmospheric influence; diffuse illumination; spectrodirectional Remote Sensing
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MDPI and ACS Style
Schopfer, J.; Dangel, S.; Kneubühler, M.; Itten, K.I. The Improved Dual-view Field Goniometer System FIGOS. Sensors 2008, 8, 5120-5140.
Schopfer J, Dangel S, Kneubühler M, Itten KI. The Improved Dual-view Field Goniometer System FIGOS. Sensors. 2008; 8(8):5120-5140.
Schopfer, Jürg; Dangel, Stefan; Kneubühler, Mathias; Itten, Klaus I. 2008. "The Improved Dual-view Field Goniometer System FIGOS." Sensors 8, no. 8: 5120-5140.