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Sensors 2016, 16(7), 1092; doi:10.3390/s16071092

Towards an Improved LAI Collection Protocol via Simulated and Field-Based PAR Sensing

1
Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623, USA
2
Department of Geography, University College London, Pearson Building, Gower Street, London WC1E 6BT, UK
*
Author to whom correspondence should be addressed.
Academic Editor: Hans Tømmervik
Received: 7 June 2016 / Revised: 5 July 2016 / Accepted: 7 July 2016 / Published: 14 July 2016
(This article belongs to the Section Remote Sensors)
View Full-Text   |   Download PDF [8032 KB, uploaded 14 July 2016]   |  

Abstract

In support of NASA’s next-generation spectrometer—the Hyperspectral Infrared Imager (HyspIRI)—we are working towards assessing sub-pixel vegetation structure from imaging spectroscopy data. Of particular interest is Leaf Area Index (LAI), which is an informative, yet notoriously challenging parameter to efficiently measure in situ. While photosynthetically-active radiation (PAR) sensors have been validated for measuring crop LAI, there is limited literature on the efficacy of PAR-based LAI measurement in the forest environment. This study (i) validates PAR-based LAI measurement in forest environments, and (ii) proposes a suitable collection protocol, which balances efficiency with measurement variation, e.g., due to sun flecks and various-sized canopy gaps. A synthetic PAR sensor model was developed in the Digital Imaging and Remote Sensing Image Generation (DIRSIG) model and used to validate LAI measurement based on first-principles and explicitly-known leaf geometry. Simulated collection parameters were adjusted to empirically identify optimal collection protocols. These collection protocols were then validated in the field by correlating PAR-based LAI measurement to the normalized difference vegetation index (NDVI) extracted from the “classic” Airborne Visible Infrared Imaging Spectrometer (AVIRIS-C) data ( R 2 was 0.61). The results indicate that our proposed collecting protocol is suitable for measuring the LAI of sparse forest (LAI < 3–5 ( m 2 / m 2 )). View Full-Text
Keywords: HyspIRI; AVIRIS; DIRSIG; leaf area index; photosynthetically active radiation HyspIRI; AVIRIS; DIRSIG; leaf area index; photosynthetically active radiation
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Yao, W.; Kelbe, D.; Leeuwen, M.V.; Romanczyk, P.; Aardt, J.V. Towards an Improved LAI Collection Protocol via Simulated and Field-Based PAR Sensing. Sensors 2016, 16, 1092.

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