Measuring Leaf Equivalent Water Thickness of Short-Rotation Coppice Willow Canopy Using Terrestrial Laser Scanning

2019 ◽  
Author(s):  
Ahmed Elsherif ◽  
Rachel Gaulton ◽  
Jon Mills
Keyword(s):  
Laser Scanning ◽  
Terrestrial Laser Scanning ◽  
Short Rotation Coppice ◽  
Short Rotation ◽  
Equivalent Water Thickness

scholarly journals THE POTENTIAL OF DUAL-WAVELENGTH TERRESTRIAL LASER SCANNING IN 3D CANOPY FUEL MOISTURE CONTENT MAPPING

2019 ◽  
Vol XLII-2/W13 ◽  
pp. 975-979
Author(s):  
A. Elsherif ◽  
R. Gaulton ◽  
J. P. Mills
Keyword(s):  
Moisture Content ◽  
Laser Scanning ◽  
Water Status ◽  
Terrestrial Laser Scanning ◽  
Dual Wavelength ◽  
Fuel Moisture ◽  
Intensity Data ◽  
Equivalent Water Thickness ◽  
Vertical Heterogeneity ◽  
Fuel Moisture Content

<p><strong>Abstract.</strong> Terrestrial laser scanning (TLS) instruments have been widely utilized in measuring vegetation canopy structural parameters, being capable of providing high density point clouds. However, less attention has been paid to using TLS intensity data in estimating vegetation biochemical attributes, and calculating water status metrics, that can help in early detection of vegetation stress and risk of wildfire. Water status metrics, such as the leaf Equivalent Water Thickness (EWT) and the Fuel Moisture Content (FMC), are being commonly estimated from optical remote sensing data. However, such estimates mainly reflect the water status of canopy top and ignore the vertical heterogeneity of water content distribution within the canopy. The estimates are also affected by canopy structure and understory reflectance. Such limitations can potentially be addressed using TLS intensity data, as observations are performed in three dimensions (3D). This study therefore investigated the potential of using dual-wavelength TLS intensity data to estimate FMC in 3D. The calculated Normalized Difference Index (NDI) of 808 nm near infrared and 1550 nm shortwave infrared wavelengths was found to be correlated to FMC at leaf level for four different tree species. The correlation was moderate, and the relationships were not consistent between species. NDI was subsequently used to estimate FMC at canopy level in seven trees in a small tree plot with an average error &amp;lt;&amp;thinsp;5&amp;thinsp;%. The 3D estimates of FMC revealed vertical heterogeneity in all trees measured, which varied between species and also between trees from the same species.</p>

scholarly journals Four Dimensional Mapping of Vegetation Moisture Content Using Dual-Wavelength Terrestrial Laser Scanning

2019 ◽  
Vol 11 (19) ◽  
pp. 2311 ◽  
Author(s):  
Ahmed Elsherif ◽  
Rachel Gaulton ◽  
Jon Mills
Keyword(s):  
Laser Scanning ◽  
Terrestrial Laser Scanning ◽  
Remote Sensing Data ◽  
Three Dimensions ◽  
Optical Remote Sensing ◽  
Canopy Reflectance ◽  
Vertical Profiles ◽  
Biochemical Traits ◽  
Equivalent Water Thickness ◽  
Vertical Heterogeneity

Recently, terrestrial laser scanning (TLS) has shown potential in measuring vegetation biochemical traits in three dimensions (3D) by using reflectance derived from backscattered intensity data. The 3D estimates can provide information about the vertical heterogeneity of canopy biochemical traits which affects canopy reflectance but cannot be measured from spaceborne and airborne optical remote sensing data. Leaf equivalent water thickness (EWT), a metric widely used in vegetation health monitoring, has been successfully linked to the normalized difference index (NDI) of near and shortwave infrared wavelengths at the leaf level. However, only two previous studies have linked EWT to NDI at the canopy level in field campaigns. In this study, an NDI consisting of 808 and 1550 nm wavelengths was used to generate 3D EWT estimates at the canopy level in a broadleaf mixed-species tree plot during and after a heatwave. The relative error in EWT estimates was 6% across four different species. Temporal changes in EWT were measured, and the accuracy varied between trees, a factor of the errors in EWT estimates on both dates. Vertical profiles of EWT were generated for six trees and showed vertical heterogeneity and variation between species. The change in EWT vertical profiles during and after the heatwave differed between trees, demonstrating that trees reacted in different ways to the drought condition.

scholarly journals On the structural complexity of central European agroforestry systems: a quantitative assessment using terrestrial laser scanning in single-scan mode

2021 ◽  
Vol 95 (4) ◽  
pp. 669-685
Author(s):  
Dominik Seidel ◽  
Melissa Stiers ◽  
Martin Ehbrecht ◽  
Maik Werning ◽  
Peter Annighöfer
Keyword(s):  
Central Europe ◽  
Laser Scanning ◽  
Agricultural Landscape ◽  
Structural Complexity ◽  
Terrestrial Laser Scanning ◽  
Agroforestry Systems ◽  
Ecosystem Functions ◽  
Christmas Tree ◽  
Canopy Openness ◽  
Short Rotation

AbstractAgroforestry systems provide important ecosystem functions and services. They have the potential to enrich agricultural monocultures in central Europe with structural elements otherwise absent, which is expected to be accompanied by a surplus of ecosystem functions. Here we used quantitative measures derived from terrestrial laser scanning in single-scan mode to describe the structural complexity, the canopy openness, the foliage height diversity and the understory complexity of four common agroforest systems in central Europe. We accessed silvopasture systems with grazing ponies and cattle as well as fellow deer, short rotation forests with agricultural use between the tree rows, tree orchards with grazing sheep and Christmas tree plantations on which chickens forage. As a reference, we used data for 65 forest sites across Germany, representing different forest types, various dominant tree species, stand ages and management systems. We found that overall stand structural complexity is ranked as follows: forest > silvopasture systems > short rotation forest > tree orchard > Christmas tree plantation. Consequently, if overall structural complexity of an agricultural landscape shall be enriched, there is now strong evidence on how this may be achieved using agroforests. However, if the focus lies on selected structures that serve specific functions, e.g. dense understory to provide animal shelter, specific types of agroforests may be chosen and the ranking in overall structural complexity may be less important.

scholarly journals DUAL-WAVELENGTH TERRESTRIAL LASER SCANNING AS A CALIBRATION TOOL FOR SATELLITE ESTIMATION OF FOREST CANOPY MOISTURE CONTENT

2020 ◽  
Vol V-3-2020 ◽  
pp. 215-220
Author(s):  
A. Elsherif ◽  
R. Gaulton ◽  
J. P. Mills
Keyword(s):  
Moisture Content ◽  
Laser Scanning ◽  
Forest Canopy ◽  
Terrestrial Laser Scanning ◽  
Dual Wavelength ◽  
Forest Plot ◽  
Calibration And Validation ◽  
Equivalent Water Thickness ◽  
Vertical Heterogeneity ◽  
Estimation Models

Abstract. Satellites can estimate forest canopy moisture content at the landscape level, and thus have been widely utilized in forest health monitoring. However, the calibration and validation of the estimation models can be challenging. Collecting a sufficient number of leaf samples from the canopy top layers in sampling plots that match the pixel size of the sensor is needed, which is a cost, time and effort consuming process. Dual-wavelength Terrestrial Laser Scanning (TLS) has been successfully used in estimating canopy moisture content of individual trees in three dimensions (3D) in several recent studies. Such 3D estimates, if produced at the plot level, can be used in the calibration and validation of satellite forest canopy moisture content estimation models. In this study, forest canopy moisture content, quantified as the leaf Equivalent Water Thickness (EWT), was estimated in 3D at the plot level in a mixed-species deciduous broadleaf forest plot using dual-wavelength TLS intensity data (808 nm near infrared and 1550 nm shortwave infrared wavelengths). The relative error in the EWT estimation was 6%, and the EWT point cloud revealed vertical heterogeneity in the EWT distribution. EWT was 37% higher in the canopy top layers than in the canopy bottom layers. The results obtained in this study showed that dual-wavelength TLS has the potential to be used in operational landscape-scale EWT estimation, and can be a useful tool for the calibration and validation of satellite EWT estimation models.

scholarly journals Melite Civitas Romana in 3D: Virtualization Project of the Archaeological Park and Museum of the Domus Romana of Rabat, Malta

2021 ◽  
Vol 7 (1) ◽  
pp. 51-83
Author(s):  
Davide Tanasi ◽  
Stephan Hassam ◽  
Kaitlyn Kingsland ◽  
Paolo Trapani ◽  
Matthew King ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Structured Light ◽  
Terrestrial Laser Scanning ◽  
Archaeological Site ◽  
South Florida ◽  
Virtual Museum ◽  
Current State ◽  
Structured Light Scanning ◽  
The University ◽  
Archaeological Excavations

Abstract The archaeological site of the Domus Romana in Rabat, Malta was excavated almost 100 years ago yielding artefacts from the various phases of the site. The Melite Civitas Romana project was designed to investigate the domus, which may have been the home of a Roman Senator, and its many phases of use. Pending planned archaeological excavations designed to investigate the various phases of the site, a team from the Institute for Digital Exploration from the University of South Florida carried out a digitization campaign in the summer of 2019 using terrestrial laser scanning and aerial digital photogrammetry to document the current state of the site to provide a baseline of documentation and plan the coming excavations. In parallel, structured light scanning and photogrammetry were used to digitize 128 artefacts in the museum of the Domus Romana to aid in off-site research and create a virtual museum platform for global dissemination.

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