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Terrestrial laser scanning measurements to characterise temporal changes in forest canopies

Cardozo, FAR 2011, Terrestrial laser scanning measurements to characterise temporal changes in forest canopies , PhD thesis, Salford : University of Salford.

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    Abstract

    Light detection and ranging (lidar) systems are active sensors capable of creating a permanent three-dimensional (3D) record of forest canopy structure. This 3D characterisation can provide increased accuracy for aboveground biomass estimates in high-biomass ecosystems, where passive optical sensors only provide a two-dimensional (2D) perspective. The aim of this study was to test a quantitative, accurate, and repeatable method to obtain estimates of canopy biophysical properties and monitor seasonal variations in forests by using multi-temporal terrestrial laser scanner (TLS) data. This research is one of the first detailed multi-temporal terrestrial lidar studies undertaken anywhere in the world. The study site chosen for this research was Delamere Forest, located in Cheshire, Northwest England. TLS data on vegetation structure were acquired for seven sampling plots, comprising two broad-leaf and five conifer stands, between March 2008 and April 2009. Canopy directional gap fractions were derived from the TLS datasets collected and compared with estimates derived from coincident hemispherical photographs. The comparison showed that TLS gap fractions estimates were consistently lower than those estimated from hemispherical photographs. To examine this apparent difference further the potential information available from the intensity values recorded by TLS were investigated. The use of this information in the computation of gap fractions led to a better agreement between estimates derived from both sources, as well as a better understanding of how intensity values are activated within forest canopies. Estimates of other biophysical properties were also computed from the TLS data, including leaf area index, average leaf angle distributions, and clumping index. The analysis of these estimates highlighted the repeatability and consistency of the TLS measurements in comparison with corresponding results derived from the hemispherical photographs. Analysis of the TLS datasets was conducted in order to improve the understanding of the interaction between lasers and vegetation canopies. The novelty of this research is in applying a ground-based lidar sensor to characterise the structure of a range of tree canopies using intensity corrected data, and assessing the utility of estimates of biophysical properties for monitoring temporal variations in forest canopies.

    Item Type: Thesis (PhD)
    Contributors: Armitage, RP(Supervisor)
    Additional Information:
    Schools: Colleges and Schools > College of Science & Technology > School of Environment and Life Sciences
    Depositing User: Institutional Repository
    Date Deposited: 03 Oct 2012 14:34
    Last Modified: 18 Feb 2014 11:52
    URI: http://usir.salford.ac.uk/id/eprint/26605

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