Thesis subject

MSc thesis topic: Understanding occlusion in an Evergreen coniferous forest at different height levels using terrestrial LiDAR

Pointclouds of forests acquired with terrestrial LiDAR (TLS) contain information on structural properties of the forest, and individual trees. However, understory and below canopy occludes reaching the top of canopy, underrepresenting tree and forest structure at their higher levels. Still unknown how much of this canopy volume is underrepresented and how occlusion affects the estimation of tree parameters (such as tree height and crown area).

A new tower was built in the long-term monitoring site for carbon flux measurements (Loobos). This new tower is bigger than the previous one, with a base of 2.57m × 2.57m and a height of 36m (16m above the canopy). It has stairways for easy access and has platforms at several heights which allow to accommodate installation of equipment. We might be able to scan the forest surrounding structure at different levels.

The goal of this project is to understand how tree occlusion affects tree parameters and tree reconstruction. For this, a one day in Loobos is needed for data collection. Further, the student is expected to pre-process the plot and extract manually the trees. We aim to compared how occlusion affects tree canopy by comparing pointclouds of ground-only scans and scans at different heights.

Relevance

Understanding the variability of the tree parameters and volume is an indicator of the need and the intensity of the “cleaning” for tropical trees. This understanding plays a relevant role when scaling from individual trees to plot level indicators.

Objectives

  • Gain experience in data collection and pre-processing of terrestrial LiDAR
  • Compare pointclouds using ground-only plot and plots at different heights.
  • Understand how occlusion affects forest canopy.

Literature

Requirements

  • Scripting skills (e.g. R, Python, MatLab, LaTeX) are a preference
  • Basic knowledge of Cloudcompare software Completion
  • GRS-32306 Advanced Earth Observation

Theme(s): Sensing & measuring