Enhancing forest attribute prediction by considering terrain and scan
angles from Lidar point clouds: a neural network approach
Abstract
Sensitivity of lidar metrics to scan angle can affect the robustness of
area-based approach (ABA) models, and modelling the interplay of scan
geometry and terrain properties can be complex. The study hypothesises
that neural networks can manage the interplay of lidar acquisition
parameters, terrain properties, and vegetation characteristics to
improve ABA models. The study area is in Massif des Bauges Natural
Regional Park, eastern France, comprising 291 field plots in a
mountainous environment with broadleaf, coniferous, and mixed forest
types. Field plots were scanned with a high overlap from multiple flight
lines and the corresponding point clouds were considered independently
to expand the standard ABA dataset (291 observations) to create a
dataset containing 1095 independent observations. Computation of lidar,
terrain and scan metrics for each point cloud associated each
observation in the expanded dataset with the scan information in
addition to the lidar and terrain information. A multilayer perceptron
(MLP) was used to model basal area and total volume to compare the
predictions resulting from standard and expanded ABA datasets. With
expanded datasets containing lidar, terrain and scan information, the R²
for the median predictions per plot were higher (R² of 0.83 and 0.85 for
BA and Vtot) than predictions with
standard datasets(R² of 0.66(BA) and
0.71(Vtot)) containing only lidar metrics.
It also outperformed an MLP model for a dataset with lidar and terrain
information (R² of 0.77 (BA and
Vtot)). The MLP performed better than RF
regression, which could not sufficiently exploit additional terrain and
scan information.