site harvard hemlock

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Site Harvard Hemlock Site 305 Site Harvard EMS tower The LAI estimates are impacted by changes in the occlusion effect at the different scales. 75m is considered as the appropriate scale due to the layout of the EVI scans. Modeled G vs. G=0.5: more work is needed to define the transition between the two in intermediate sites Retrieving Leaf Area Index and Foliage Profiles through Voxelized 3-D Forest Reconstruction Using Terrestrial Full Waveform Dual-Wavelength Echidna® Lidar (DWEL) Alan Strahler 1 , Xiaoyuan Yang 2, 3 , Crystal Schaaf 3 , Zhan Li 1 , Zhuosen Wang 3 , Tian Yao 4 , Feng Zhao 5 , Edward Saenz 3 , Ian Paynter 3 , Ewan Douglas 1 , Supriya Chakrabarti 6 , Timothy Cook 6 , Jason Martel 6 , Glenn Howe 6 , David Jupp 7 , Darius Culvenor 8 , Glenn Newnham 9 , Jenny Lovell 10 1 Boston University, Boston, MA, USA; 2 Sandia National Laboratory, Livermore, CA, USA; 3 University of Massachusetts Boston, Boston, MA, USA; 4 Montclair State University, Montclair, NJ, USA; 5 University of Maryland, College Park, MD, USA; 6 University of Massachusetts Lowell, Lowell, MA, USA; 7 CSIRO Marine and Atmospheric Research, Canberra ACT, Australia; 8 Environmental Sensing Systems, Melbourne, Victoria 3000, Australia; 9 CSIRO Land and Water, Clayton South, Victoria, Australia; 10 CSIRO Marine and Atmospheric Research, Hobart, Tasmania, Australia Foliage Area Volume Density & Leaf Area Index G- function Leaf reflectance Apparent reflectance of the point Probability of gap Three-dimensional Forest Reconstruction Voxelization Voxelization transform s the irregular, unorganized cloud of data points in the 3-D forest reconstruction into volumetric datasets. Voxel Based LAI & FAVD Estimation FAVD Model for point cloud The total effective area of objects in volume V or Leaf area index: Noted: In the case of multiple observations: the average of LAI is used. Modeling Model the product from the distribution of hit values with angle in the scan data and apply the model to each hit to get LAI and FAVD profile. Horizontal fraction of canopy cover Derived value of at the hinge angle Site ID Field LAI Voxel based LAI by Diameter G=0.5 50m 75m 100m Hemlock 4.32±0.27 4.95 4.73 3.66 2.68 EMS tower 4.67±0.82 5.30 4.86 3.52 2.83 305 2.03±0.50 6.54 *5.55 4.86 2.77 Measuring and monitoring canopy biophysical parameters provide a baseline for carbon flux studies related to deforestation and disturbance in forest ecosystem. Terrestrial full-waveform lidar systems, Echidna® Validation Instrument (EVI) and its successor Dual-Wavelength Echidna® Lidar (DWEL), offer rapid, accurate, and automated characterization of forest structure (Strahler et al., 2008; Yang et al., 2013). In this study, we proposed a methodology based on voxelized 3-D forest reconstruction built from EVI and DWEL scans (Douglas et al., 2012) to directly estimate two important biophysical parameters: Leaf Area Index (LAI) and foliage profiles. Overview Site Characteristics Site ID Leading dominants Top canopy height (m) Mean DBH (m) Stem count density (ha –1 ) Above- ground biomass (t ha –1 ) Hemlock Hemlock 22.6 0.24±0.0 2 906±71 234±7 EMS Tower Red maple, red oak 26.4 0.28±0.0 2 951±69 373±36 305 Red fir 45.2 0.58±0.0 2 284±40 1215±150 While the two instruments detected the top of the canopy pretty well, LVIS sees more upper canopy component while EVI sees more lower canopy component over the same forest area. (Profiles are compared at 75 m plot diameter.) Site Harvard Hemlock Site 305 Site Harvard EMS tower Terrestrial (EVI) vs. Airborne (LVIS) Lidar Dual-Wavelength Echidna® Lidar (DWEL) The Dual-Wavelength Echidna ® Lidar (DWEL), the successor instrument to the EVI, emits simultaneous laser pulses at 1064 nm and 1548 nm wavelengths. DWEL scans provide the capability to separate hits of leaves from hits of trunks and branches because of the reduced response at 1548 nm due to water absorption by leaf cellular contents. Normalized Difference Index (NDI): (1064nm – 1548nm) / (1064 nm + 1548 nm) 1064nm 1548 nm 1064 nm 1548 nm Classification by thresholding NDI By simply thresholding NDI of each point, the range effects in the classification is largely reduced, and the trunks are differentiated from foliage/branchlets points. ,, 1 ,, ,, app t gap r f r G P r ,, ,, ,, ,, app V t gap r V LA r V f r G P r (,,) (,,) () (,,) app V t gap x yz V LA x yz G P x yz ,, base LAI LA x yz A 12 2 m ax, 2 1 2 cos 1 sin t c H H G

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Retrieving Leaf Area Index and Foliage Profiles through Voxelized 3-D Forest Reconstruction Using Terrestrial Full Waveform Dual-Wavelength Echidna® Lidar (DWEL ) - PowerPoint PPT Presentation

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Page 1: Site Harvard Hemlock

Site Harvard Hemlock

Site 305Site Harvard EMS tower

The LAI estimates are impacted by changes in the occlusion effect at the different scales. 

75m is considered as the appropriate scale due to the layout of the EVI scans.

Modeled G vs. G=0.5: more work is needed to define the transition between the two in intermediate sites

Retrieving Leaf Area Index and Foliage Profiles through Voxelized 3-D Forest Reconstruction Using Terrestrial Full Waveform Dual-Wavelength Echidna® Lidar (DWEL)

Alan Strahler1, Xiaoyuan Yang2, 3, Crystal Schaaf3, Zhan Li1, Zhuosen Wang3, Tian Yao4, Feng Zhao5, Edward Saenz3, Ian Paynter3, Ewan Douglas1, Supriya Chakrabarti6, Timothy Cook6, Jason Martel6, Glenn Howe6, David Jupp7, Darius Culvenor8, Glenn Newnham9, Jenny Lovell10

1Boston University, Boston, MA, USA; 2Sandia National Laboratory, Livermore, CA, USA; 3University of Massachusetts Boston, Boston, MA, USA; 4Montclair State University, Montclair, NJ, USA; 5University of Maryland, College Park, MD, USA; 6University of Massachusetts Lowell, Lowell, MA, USA; 7CSIRO Marine and Atmospheric Research, Canberra ACT, Australia; 8Environmental Sensing Systems, Melbourne,

Victoria 3000, Australia; 9CSIRO Land and Water, Clayton South, Victoria, Australia; 10CSIRO Marine and Atmospheric Research, Hobart, Tasmania, Australia

Foliage Area Volume Density & Leaf Area Index

, ,1, ,, ,

app

t gap

rf r

G P r

G-function Leaf reflectance

Apparent reflectance of the point

Probability of gap

Three-dimensional Forest Reconstruction

Voxelization

Voxelization transform s the irregular, unorganized cloud of data points in the 3-D forest reconstruction into volumetric datasets.

Voxel Based LAI & FAVD Estimation•FAVD Model for point cloud

•The total effective area of objects in volume V

or

•Leaf area index:

Noted: In the case of multiple observations: the average of LAI is used.

, ,, , , ,

, ,app

Vt gap

rVLA r V f rG P r

( , , )( , , )

( ) ( , , )app

Vt gap

x y zVLA x y zG P x y z

, , baseLAI LA x y z A

Modeling

Model the product from the distribution of hit values with angle in the scan data and apply the model to each hit to get LAI and FAVD profile.

1 22

max, 21 2 cos 1 sint c H HG f f

Horizontal fraction of canopy cover

Derived value of at the hinge angle

Site ID Field LAIVoxel based LAI by Diameter

G=0.550m 75m 100m

Hemlock 4.32±0.27 4.95 4.73 3.66 2.68EMS tower 4.67±0.82 5.30 4.86 3.52 2.83

305 2.03±0.50 6.54 *5.55 4.86 2.77

Measuring and monitoring canopy biophysical parameters provide a baseline for carbon flux studies related to deforestation and disturbance in forest ecosystem. Terrestrial full-waveform lidar systems, Echidna® Validation Instrument (EVI) and its successor Dual-Wavelength Echidna® Lidar (DWEL), offer rapid, accurate, and automated characterization of forest structure (Strahler et al., 2008; Yang et al., 2013). In this study, we proposed a methodology based on voxelized 3-D forest reconstruction built from EVI and DWEL scans (Douglas et al., 2012) to directly estimate two important biophysical parameters: Leaf Area Index (LAI) and foliage profiles.

Overview

Site Characteristics

Site ID Leading dominants

Top canopy height

(m)

Mean DBH (m)

Stem count density (ha–1)

Above-ground

biomass (t ha–1)

Hemlock Hemlock 22.6 0.24±0.02 906±71 234±7

EMS Tower Red maple, red oak 26.4 0.28±0.02 951±69 373±36

305 Red fir 45.2 0.58±0.02 284±40 1215±150

While the two instruments detected the top of the canopy pretty well, LVIS sees more upper canopy component while EVI sees more lower canopy component over the same forest area. (Profiles are compared at 75 m plot diameter.)

Site Harvard Hemlock

Site 305Site Harvard EMS tower

Terrestrial (EVI) vs. Airborne (LVIS) Lidar

Dual-Wavelength Echidna® Lidar (DWEL)

The Dual-Wavelength Echidna® Lidar (DWEL), the successor instrument to the EVI, emits simultaneous laser pulses at 1064 nm and 1548 nm wavelengths. DWEL scans provide the capability to separate hits of leaves from hits of trunks and branches because of the reduced response at 1548 nm due to water absorption by leaf cellular contents.

Normalized Difference Index (NDI): (1064nm – 1548nm) / (1064 nm + 1548 nm)

1064nm 1548 nm

1064 nm 1548 nm

Classification by thresholding NDI

By simply thresholding NDI of each point, the range effects in the classification is largely reduced, and the trunks are differentiated from foliage/branchlets points.