Abstract
Terrestrial laser scanning (TLS) is a high-potential technology in forest surveys. Estimating the diameters at breast height (DBH) accurately and quickly has been considered a key step in estimating forest structural parameters by using TLS technology. However, the accuracy and speed of DBH estimation are affected by many factors, which are classified into three groups in this study. We adopt an additive error model and propose a simple and common simulation method to evaluate the impacts of three groups of parameters, which include the range error, angular errors in the vertical and horizontal directions, angular step width, trunk distance, slice thickness, and real DBH. The parameters were evaluated statistically by using many simulated point cloud datasets that were under strict control. Two typical circle fitting methods were used to estimate DBH, and their accuracy and speed were compared. The results showed that the range error and the angular error in horizontal direction played major roles in the accuracy of DBH estimation, the angular step widths had a slight effect in the case of high range accuracy, the distance showed no relationship with the accuracy of the DBH estimation, increasing the scanning angular width was relatively beneficial to the DBH estimation, and the algebraic circle fitting method was relatively fast while performing DBH estimation, as is the geometrical method, in the case of high range accuracy. Possible methods that could help to obtain accurate and fast DBH estimation results were proposed and discussed to optimize the design of forest inventory experiments.
Highlights
Forests are the dominant terrestrial ecosystem on the Earth and are closely related to human production and life [1]
Our observations showed that whether an increase in the thickness improved the accuracy of the diameters at breast height (DBH) estimation depended on the angular step widths (Figure 11)
The main goal of this study was to evaluate the impacts of error parameters, scanning parameters, trunk slice parameters, and circle fitting methods on DBH estimation
Summary
Forests are the dominant terrestrial ecosystem on the Earth and are closely related to human production and life [1]. Monitoring forest biomass is one of the most important ways to understand the changes in forests and analyze the relationship between humans and the natural environment. As the dominant part of forest biomass, tree biomass can help to estimate and verify forest biomass. The diameter of a tree at breast height (DBH) is one of the most common and important field measurements in forest inventories and is indispensable for accurately estimating timber volume and tree biomass. DBH can be manually measured by using a girthing tape or calipers. Some new methods have been used to measure DBH, such as electrical calipers and laser scanners [2,3]
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