Dual-wavelength terrestrial laser scanning for measurement of forest canopy structure and health

Northern Research Station, Roslin.
5 December 2013, 2-3pm.

This presentation described the development and testing of the Salford Advanced Laser Canopy Analyser.

It presented the initial results of on-going experiments determining the potential for foliage moisture content estimation from SALCA data at leaf and canopy scales and gave an over-view of a recent international TLS inter-comparison and calibration exercise, involving over 30 scientists from the US, Australia and the UK, held in August 2013 in Brisbane, Australia.

The inter-comparison, including three custom-built research instruments and two commercial scanners, was accompanied by extensive ground measurements and airborne LiDAR data collection and will help to determine the accuracy with which forest structure parameters such as LAI can be obtained through a number of different approaches as well as the value of dual-wavelength and full-waveform information for forest applications.

Terrestrial laser scanning (TLS) has been shown to provide valuable information on forest canopy structure at plot scales. Newly developed instruments, such as the SALCA instrument, which operates using two laser wavelengths, can allow information on the three-dimensional structure and reflectance properties of forest canopies to be acquired with unprecedented detail, facilitating use in modelling, validation of remote sensing or biomass measurement. The two wavelengths at which SALCA operates (1064 nm an 1545 nm), allow calculation of a ratio, based on reflectance properties, that is sensitive to leaf moisture content, an indicator of tree drought stress, disease and wildfire risk, and facilitates the separation of woody material and foliage in the scan, improving estimation of LAI.

Dr Rachel Gaulton obtained a PhD, in remote sensing for continuous cover forestry, in 2009, from the University of Edinburgh. Her work, a NERC CASE project with the Forestry Commission, explored the potential of airborne LiDAR and hyperspectral data for monitoring canopy gaps and disturbance in continuous cover stands. Following her PhD, she undertook postdoctoral research at the University of British Columbia, Vancouver, Canada, examining the fusion of satellite imagery for high temporal and spatial resolution mapping of forest disturbance and the integration of satellite-derived information for spatial prediction of forest volume on regional scales. During a subsequent postdoctoral research fellowship at Salford University, she contributed to the initial development and testing of the SALCA terrestrial laser scanner. In 2011, she obtained a lectureship in remote sensing at Newcastle University in the School of Civil Engineering and Geosciences. She is PI of a current NERC grant examining the potential of dual-wavelength laser scanning for forest health monitoring and a Royal Society research grant examining the use of low-cost thermal imagers on unmanned aerial vehicles for forest health monitoring.