研究目的
The aim of this study was to design an appropriate CRP method in order to create 3D point clouds of individual trees. Furthermore, we estimated the diameter and perimeter of individual trees with different types of bark, at different heights on the tree stem using a digital single-lens reflex (DSLR) camera with a non-fisheye lens and a fisheye lens, separately.
研究成果
CRP is suitable for generating 3D point clouds of individual trees with a high accuracy of diameter and perimeter estimations of the tree trunk. The tree species affected the accuracy significantly with regard to the perimeter and diameter estimations. The estimation accuracy of the perimeter and diameter of the trees was highly promising for the monitoring of annual tree trunk increment.
研究不足
The study was limited to four tree species and three height levels on the tree stem. The distance from the tree was maintained at 3 m, which might not cover all possible scenarios in forestry applications.
1:Experimental Design and Method Selection
The study focused on the reconstruction of trees separately within the forest stand, investigating the influence of camera lens, tree species, and height of diameter on the accuracy of the tree perimeter and diameter estimation.
2:Sample Selection and Data Sources
Four tree species (Fagus sylvatica L., Quercus petraea (Matt.) Liebl., Picea abies (L.) H. Karst. and Abies alba Mill.) were chosen. The perimeters and diameters were measured at three height levels (0.8 m, 1.3 m, and 1.8 m).
3:List of Experimental Equipment and Materials
A DSLR camera, Canon 70D with a CMOS sensor and 20.2-megapixel resolution, was used with two different lenses: Canon EF 35 mm f/2 IS USM (non-fisheye) and Canon EF 8–15 mm f/4L Fisheye USM (fisheye).
4:Experimental Procedures and Operational Workflow
The data acquisition followed a circle around the tree at a 3 m radius. Images were processed into scaled and oriented point clouds using Agisoft PhotoScan Professional 1.2.6 software.
5:Data Analysis Methods
The RMSE of the perimeter and diameter estimation was calculated. The factorial analysis of variance (ANOVA) was performed to detect the effects of lens, tree species, and height of measurements on the estimation error.
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