Abstract
Abstract. The objective of this work was to create a method to measure stem attributes of standing trees on field plots in the forest using terrestrial photogrammetry. The primary attributes of interest are the position and the diameter at breast height (DBH). The developed method creates point clouds from images from three or more calibrated cameras attached to a calibrated rig. SIFT features in multiple images in combination with epipolar line filtering are used to make high quality matching in images with large amounts of similar features and many occlusions. After projection of the point cloud to a simulated ground plane, RANSAC filtering is applied, followed by circle fitting to the remaining points. To evaluate the algorithm, a camera rig of five Canon digital system cameras with a baseline of 123 cm and up to 40 cm offset in height was constructed. The rig was used in a field campaign at the Remningstorp forest test area in southern Sweden. Ground truth was collected manually by surveying and manual measurements. Initial results show estimated tree stem diameters within 10% of the ground truth. This suggest that terrestrial photogrammetry is a viable method to measure tree stem diameters on circular field plots.
Highlights
1.1 Background and AimThe forestry industry requires information, such as species, stem diameter, volume and height, about trees in the forests for management planning
These preliminary results indicate that this method is viable for estimation of stem attributes in circular field plots
The current method appears to be sensitive to outliers remaining after the RANSAC filtering
Summary
The forestry industry requires information, such as species, stem diameter, volume and height, about trees in the forests for management planning. The information has been collected by manual inventory using calipers to measure stem diameters. The inventory in Sweden is usually done on circular field plots with a radius of 10 meters. From this kind of samples larger stocks of forests are estimated. The process of manually measuring the trees is labor intensive, and the planners want as much and as reliable information as possible. A method to estimate tree stem diameter and position using terrestrial photogrammetry and image analysis is proposed
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