Abstract
Parameter estimation and effective tree trunk model establishment are significant to tree biomass measurements and three-dimensional (3D) reconstruction. In this study, we proposed a trunk model establishment and parameter estimation method for a single tree through multistation terrestrial laser scanning (TLS). This approach obtains a more accurate and dense point cloud and yields several improvements. First, to correct the tree position, the angle between the trunk centreline and the vertical line was extracted to normalize the tree point clouds. Subsequently, some tree model parameters were accurately calculated. The tree height was extracted based on individual differences rather than directly adopting the Digital Elevation Model (DEM) model; The B-Spline curve fitting was added to the diameters at breast height (DBH) measure, which better determined the shape of the DBH compared with circle fitting; The CBH was measured by multi-view voxel projection instead of Single-view fixed threshold segmentation, which confirmed the position of the CBH more accurately. To highlight the effectiveness and pertinence of the proposed method, we analysed three plots that the proposed method can achieve more accurate results, where the mean relative error (MRE) of the tree height, DBH and CBH were 1.89%, 1.74% and 2.91% satisfying the accuracy standard specified by the technical indicators (±5%). The experimental results validate the trunk model accuracy and the effectiveness of the parameter measurements (close to the field measurements). The proposed method is significantly different from the accuracy of the previous method. The proposed method has the best accuracy in Multistation Terrestrial Laser Scanning. Hence the proposed method has outstanding performance in the high-precision extraction of trunk parameters and the construction of trunk models which will perform forest inventory and construction of virtual forest more accurately.
Highlights
Different from the method in which the tree morphological parameters are collected in a single way [61], our trunk parameter extraction method is combined with multiple methods, which is a suitable method for each parameter
The laser altimeter cannot handle the errors caused by the tilt when it encounters tree growth
We used the curve to fit the abnormal points to further improve the fitting of the diameters at breast height (DBH) curve by the B-spline method
Summary
A. BACKGROUND Estimation of trunk parameters such as tree diameter or height is of great significance to tree growth state and biomass estimation analyses. The tree volume and biomass allometric equations have been established with extensive destructive sampling of trees [1]. Tree models require many dependable samples [2], but the number and spatial extent of samples collected in the field are always limited. Primarily stem from the significant cost and labour expense involved in destructive sampling. With the rapid development of measurement equipment, the non-destructive measurement method has been widely used in tree surveying, which reduces the labour cost and avoids considerable damage
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