Universität zu Köln

Aasen, Helge ORCID: 0000-0003-4343-0476 and Bolten, Andreas ORCID: 0000-0003-1287-9705 (2018). Multi-temporal high-resolution imaging spectroscopy with hyperspectral 2D imagers - From theory to application. Remote Sens. Environ., 205. S. 374 - 390. NEW YORK: ELSEVIER SCIENCE INC. ISSN 1879-0704

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Abstract

With the increasing availability of spectral sensors and consumer-grade data processing software, a democratization of imaging spectroscopy is taking place. In particular, novel lightweight 2D spectral imagers in combination with UAVs are increasingly being adapted for imaging spectroscopy. In contrast to traditional line scanners, these sensors capture spectral information as a 2D image within every exposure. With computer vision algorithms embedded in consumer grade software packages, these data can be processed to hyperspectral digital surface models that hold spectral and 3D spatial information in very high resolution. To understand the spectral signal, however, one must comprehend the complexity of the capturing and data processing process in imaging spectroscopy with 2D imagers. This study establishes the theoretical background to comprehend the properties of spectral data acquired with 2D imagers and investigates how different data processing schemes influence the data. To improve the interpretability of a spectral signal derived for an area of interest (AOI, the specific field of view is introduced as a concept to understand the composition of pixels and their angular properties used to characterize a specific AOI within a remote sensing scene. These considerations are applied to a multi-temporal field study carried out under different illumination conditions in a barley field phenotyping experiment. It is shown that data processing significantly affects the angular properties of the spectral data and influences the apparent spectral signature. The largest differences are found in the red domain, where the signal differs by approximately 10% relative to a single nadir image. Even larger differences of approximately 14% are found in comparison with ground-based non-imaging field spectrometer measurements. The differences are explained by investigating the interaction between the angular properties of the data and canopy anisotropy, which are wavelength and growth stage dependent. Additionally, it is shown that common vegetation indices cannot normalize the differences and that the retrieval of chlorophyll is affected. In conclusion, this study helps to understand the process of imaging spectroscopy with 2D imagers and provides recommendations for future missions.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Aasen, Helge UNSPECIFIED orcid.org/0000-0003-4343-0476 UNSPECIFIED Bolten, Andreas UNSPECIFIED orcid.org/0000-0003-1287-9705 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-196690
DOI:	10.1016/j.rse.2017.10.043
Journal or Publication Title:	Remote Sens. Environ.
Volume:	205
Page Range:	S. 374 - 390
Date:	2018
Publisher:	ELSEVIER SCIENCE INC
Place of Publication:	NEW YORK
ISSN:	1879-0704
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language FIELD-OF-VIEW; VEGETATION INDEXES; CHLOROPHYLL CONTENT; REFLECTANCE; PHOTOGRAMMETRY; FLUORESCENCE; CAMERAS; BIOMASS; ACQUISITION; TEMPERATURE Multiple languages Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/19669