Vertical Optical Scanning with Panoramic Vision for Tree Trunk Reconstruction

Abstract

This paper presents a practical application of a technique that uses a vertical optical flow with a fisheye camera to generate dense point clouds from a single planimetric station. Accurate data can be extracted to enable the measurement of tree trunks or branches. The images that are collected with this technique can be oriented in photogrammetric software (using fisheye models) and used to generate dense point clouds, provided that some constraints on the camera positions are adopted. A set of images was captured in a forest plot in the experiments. Weighted geometric constraints were imposed in the photogrammetric software to calculate the image orientation, perform dense image matching, and accurately generate a 3D point cloud. The tree trunks in the scenes were reconstructed and mapped in a local reference system. The accuracy assessment was based on differences between measured and estimated trunk diameters at different heights. Trunk sections from an image-based point cloud were also compared to the corresponding sections that were extracted from a dense terrestrial laser scanning (TLS) point cloud. Cylindrical fitting of the trunk sections allowed the assessment of the accuracies of the trunk geometric shapes in both clouds. The average difference between the cylinders that were fitted to the photogrammetric cloud and those to the TLS cloud was less than 1 cm, which indicates the potential of the proposed technique. The point densities that were obtained with vertical optical scanning were 1/3 less than those that were obtained with TLS. However, the point density can be improved by using higher resolution cameras.

Structure from Motion Photogrammetry in Forestry: a Review

“…Most investigations on the use of terrestrial SfM were performed reconstructing single trees (i.e. not the entire forest plot) [16,76,[79][80][81][82][83]. In those studies, DBH was the most frequently estimated parameter and often compared with TLS data for accuracy assessment.…”

3D Imaging of CRP and Ultrasonic Tomography to Detect Decay in a Living Adult Holm Oak (Quercus ilex L.) in Sardinia (Italy)

“…In the last few decades, 3D modelling of trees has become more and more important in detecting their biometrical and physical parameters in forests as well as for in situ tree reconstruction in places like forest stands, plots, and tree levels [1][2][3][4][5]. Traditional fieldbased sampling measurement applied to tree analysis can be classified into non-contact methods (with the aid of laser electronic rangefinders, EDMs, levelling, etc.)…”

The Potential of Low-Cost 3D Imaging Technologies for Forestry Applications: Setting a Research Agenda for Low-Cost Remote Sensing Inventory Tasks

“…Studies that captured inventory metrics at a plot scale utilising CRP methodologies have used either moving capture approaches, using a stop-and-go or a mobile method, or a stationary approach, where images were captured from the centre of the plot, only capturing partial-stem views but reducing overall capture and processing times [40,61]. Regarding the former, Mokroš et al [62] compared a series of capture methodologies based on those previously defined by Liang et al [63] and Liang et al [64], provided the most accurate stem measurements using a vertical camera orientation and navigating around the plot exterior facing inwards, with two central transects facing out.…”