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Options for estimating horizontal visibility in hemiboreal forests using sparse airborne laser scanning data and forest inventory data

Authors
  • Lang, Mait1, 2
  • Vennik, Kersti3
  • Põldma, Andrus3
  • Nilson, Tiit1
  • 1 University of Tartu, Estonia , (Estonia)
  • 2 Estonian University of Life Sciences, Kreutzwaldi 5 , (Estonia)
  • 3 Military Academy, Riia 12 , (Estonia)
Type
Published Article
Journal
Forestry Studies
Publisher
Sciendo
Publication Date
Mar 11, 2021
Volume
73
Issue
1
Pages
125–135
Identifiers
DOI: 10.2478/fsmu-2020-0019
Source
De Gruyter
Keywords
License
Green

Abstract

Horizontal visibility v in hemiboreal forest transects was measured in the field and then predicted, both from forest inventory (FI) data and from airborne laser scanning (ALS) data. Stand density N and mean diameter at breast height D were used as arguments in an FI predictive model assuming Poisson distribution of trees on a horizontal plane. It was found that a lack of FI data on forest regrowth and understorey trees caused v to be overestimated. Point cloud metrics of sparse ALS data from summer 2017 and spring 2019 were used as predictive variables for v in regression models. The best models were based on three variables: the 10th percentile of the point cloud height distribution, relative density of returns in a horizontal layer ranging 0.7–2.2 m above the ground, and canopy cover. The models had a coefficient of determination of up to 67% and a residual standard error of less than 25 m. In forests in which fertile soil produces rapid height growth of understorey woody vegetation after recent thinning, visibility was found to be substantially overestimated because the understorey was not detected by the lidar measurements.

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