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Correction of the diffuse influence in spectrodirectional measurements


Schopfer, Jürg T; Dangel, Stefan; Kaiser, Johannes W; Kneubühler, Mathias; Nieke, Jens; Schaepman-Strub, Gabriela; Schaepman, Michael E; Itten, Klaus I (2004). Correction of the diffuse influence in spectrodirectional measurements. In: International Radiation Symposium, Busan, Korea, 23 August 2004 - 28 August 2004, 371-374.

Abstract

Spectro-directional surface measurements can either be performed in the field or within a laboratory setup. Laboratory measurements have the advantage of constant illumination and neglectable atmospheric disturbances. On the other hand, artificial light sources are usually less parallel and less homogeneous than the clear sky solar illumination. To account for these differences and for determining for which targets a replacement of field by laboratory experiments is indeed feasible, a quantitative comparison is a prerequisite. Currently, there exist no systematic comparisons of field and laboratory measurements using the same targets. In this study we concentrate on the difference in spectro-directional field and laboratory data of the same target due to diffuse illumination and applied a correction term proposed by (Martonchik, 1994). Spectro-directional data were obtained with a GER3700 spectroradiometer. Additionally, a MFR sun photometer directly observed the total incoming diffuse irradiance. In the laboratory, a 1000W brightness-stabilized quartz tungsten halogen lamp was used. For the first direct comparison of field and laboratory measurements, we used an inert and highly anisotropic target with high angular anisotropy. Analysis showed that the diffuse illumination in the field is leading to a higher total reflectance and less pronounced angular anisotropy.

Abstract

Spectro-directional surface measurements can either be performed in the field or within a laboratory setup. Laboratory measurements have the advantage of constant illumination and neglectable atmospheric disturbances. On the other hand, artificial light sources are usually less parallel and less homogeneous than the clear sky solar illumination. To account for these differences and for determining for which targets a replacement of field by laboratory experiments is indeed feasible, a quantitative comparison is a prerequisite. Currently, there exist no systematic comparisons of field and laboratory measurements using the same targets. In this study we concentrate on the difference in spectro-directional field and laboratory data of the same target due to diffuse illumination and applied a correction term proposed by (Martonchik, 1994). Spectro-directional data were obtained with a GER3700 spectroradiometer. Additionally, a MFR sun photometer directly observed the total incoming diffuse irradiance. In the laboratory, a 1000W brightness-stabilized quartz tungsten halogen lamp was used. For the first direct comparison of field and laboratory measurements, we used an inert and highly anisotropic target with high angular anisotropy. Analysis showed that the diffuse illumination in the field is leading to a higher total reflectance and less pronounced angular anisotropy.

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Additional indexing

Item Type:Conference or Workshop Item (Paper), not refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Geography
07 Faculty of Science > Grid Computing Competence Center
Dewey Decimal Classification:910 Geography & travel
Language:English
Event End Date:28 August 2004
Deposited On:26 Aug 2014 15:59
Last Modified:08 Dec 2017 07:02
Publisher:s.n.
ISBN:0-937-194-49-2
Official URL:http://www.irc-iamas.org/symposium/

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