Angular reflectance of leaves with a dual-wavelength terrestrial lidar and its implications for leaf-bark separation and leaf moisture estimation

Hancock, S, Gaulton, R and Danson, FM 2017, 'Angular reflectance of leaves with a dual-wavelength terrestrial lidar and its implications for leaf-bark separation and leaf moisture estimation' , IEEE Transactions on Geoscience and Remote Sensing .

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Abstract

A new generation of multi-wavelength lidars offer the potential to measure the structure and biochemistry of vegetation simultaneously, using range resolved spectra indices to overcome the confounding effects in passive optical measurements. However, the reflectance of leaves depends on angle of incidence and if this dependence varies between wavelengths, the resulting spectral indices will also vary with angle of incidence, complicating their use in separating structural and biochemical effects in vegetation canopies. The SALCA dualwavelength terrestrial laser scanner (Salford Advanced Laser Canopy Analyser) was used to measure the angular dependence of reflectance for a range of leaves at the wavelengths used by the new generation of multi-wavelength lidars, 1063 nm and 1545nm, as used by SALCA, DWEL and the Optech Titan. The influence of the angle of incidence on the Normalised Difference Index of these wavelengths (NDI) was also assessed. The reflectance at both wavelengths depended on the angle of incidence, was non-Lambertian and could be well modelled as a cosine. The change in NDI with leaf angle of incidence was small compared to the observed difference in NDI between fresh and dry leaves and between leaf and bark. Therefore it is concluded that angular effects will not significantly impact leaf moisture retrievals or prevent leaf/bark separation for the wavelengths used in the new generation of 1063 nm and 1545 nm multi-wavelength lidars.

Item Type: Article
Schools: Schools > School of Environment and Life Sciences > Ecosystems and Environment Research Centre
Journal or Publication Title: IEEE Transactions on Geoscience and Remote Sensing
Publisher: Institute of Electrical and Electronics Engineers
ISSN: 0196-2892
Related URLs:
Funders: NERC
Depositing User: FM Danson
Date Deposited: 02 Feb 2017 14:46
Last Modified: 19 Oct 2017 14:46
URI: http://usir.salford.ac.uk/id/eprint/41315

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