Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 419119
Title A new lab facility for measuring bidirectional reflectance/emittance distribution functions of soils and canopies
Author(s) Clevers, J.G.P.W.; Bartholomeus, H.; Schaepman, M.E.; Schaepman-Strub, G.; Jalink, H.; Schoor, R. van der; Jong, A. de; Uiterwijk, M.
Source In: Proceedings 7th EARSeL Workshop of the Special Interest Group in Imaging Spectroscopy, Edinburgh, Scotland, UK, 11 - 13 April, 2011. - Edinburgh, UK : EARSeL - p. 10 - 10.
Event Edinburgh, UK : EARSeL 7th EARSeL Workshop of the Special Interest Group in Imaging Spectroscopy, Edinburgh, Scotland, UK, 2011-04-11/2011-04-13
Department(s) Laboratory of Geo-information Science and Remote Sensing
Nature Conservation and Plant Ecology
WUR GTB Tuinbouw Technologie
CGI - Geo-information Communication
CGI - Spatial Models and Knowledge Systems
PE&RC
Publication type Contribution in proceedings
Publication year 2011
Abstract Recently, a laboratory measurement facility has been realized for assessing the anisotropic reflectance and emittance behaviour of soils, leaves and small canopies under controlled illumination conditions. The facility consists of an ASD FieldSpec 3 spectroradiometer covering the spectral range from 350 – 2500 nm at 1 nm spectral sampling interval. The spectroradiometer is deployed using a fiber optic cable with either a 1°, 8° or 25° instantaneous field of view (IFOV). These measurements can be used to assess the plant pigment (chlorophyll, xanthophyll, etc.) and non-pigment system (water, cellulose, lignin, nitrogen, etc.). The thermal emittance is measured using a NEC TH9100 Infrared Thermal Imager. It operates in a single band covering the spectral range from 8 – 14 mm with a resolution of 0.02 K. Images are 320 (H) by 240 (V) pixels with an IFOV of 1.2 mrad. A 1000 W Quartz Tungsten Halogen (QTH) lamp is used as illumination source, approximating the radiance distribution of the sun. This one is put at a fixed position during a measurement session. Multi-angular measurements are achieved by using a robotic positioning system allowing to perform either reflectance or emittance measurements over almost a complete hemisphere. The hemisphere can be sampled continuously between 0° and 80° from nadir and up to a few degrees from the hot-spot configuration (depending on the IFOV of the measurement device) for a backscattering target. Measurement distance to targets can be varied between 0.25 and 1 m, although with a distance of more than 0.6 m it is not possible to cover the full hemisphere. The goal is to infer the BRDF (bidirectional reflectance distribution function) and BTDF (bidirectional thermal distribution function) from these multi-angular measurements for various surface types (like soils, agricultural crops, small tree canopies and artificial objects) and surface roughness. The steering of the robotic arm and the reading of the spectroradiometer and the thermal camera are all fully automated.
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