Accuracy of Reconstruction of the Tree Stem Surface Using Terrestrial Close-Range Photogrammetry

Abstract

Airborne laser scanning (ALS) allows for extensive coverage, but the accuracy of tree detection and form can be limited. Although terrestrial laser scanning (TLS) can improve on ALS accuracy, it is rather expensive and area coverage is limited. Multi-view stereopsis (MVS) techniques combining computer vision and photogrammetry may offer some of the coverage benefits of ALS and the improved accuracy of TLS; MVS combines computer vision research and automatic analysis of digital images from common commercial digital cameras with various algorithms to reconstruct three-dimensional (3D) objects with realistic shape and appearance. Despite the relative accuracy (relative geometrical distortion) of the reconstructions available in the processing software, the absolute accuracy is uncertain and difficult to evaluate. We evaluated the data collected by a common digital camera through the processing software (Agisoft PhotoScan ©) for photogrammetry by comparing those by direct measurement of the 3D magnetic motion tracker. Our analyses indicated that the error is mostly concentrated in the portions of the tree where visibility is lower, i.e., the bottom and upper parts of the stem. For each reference point from the digitizer we determined how many cameras could view this point. With a greater number of cameras we found increasing accuracy of the measured object space point positions (as expected), with a significant positive change in the trend beyond five cameras; when more than five cameras could view this point, the accuracy began to increase more abruptly, but eight cameras or more provided no increases in accuracy. This method allows for the retrieval of larger datasets from the measurements, which could improve the accuracy of estimates of 3D structure of trees at potentially reduced costs.

Examination of the Potential of Terrestrial Laser Scanning and Structure-from-Motion Photogrammetry for Rapid Nondestructive Field Measurement of Grass Biomass

“…Improved digital camera technology and computing capabilities enable rapid SfM implementation. SfM has been used to estimate tree heights and stem diameters [32][33][34][35], tree volumes [36,37], shrub heights [38], and crop heights [39][40][41]. However, no studies to our knowledge have used SfM to assess grass biomass.…”

Relasphone—Mobile and Participative In Situ Forest Biomass Measurements Supporting Satellite Image Mapping

“…However, TLS is expensive, not easily portable and requires an expertly-trained operator. Terrestrial photogrammetry in digital optical images was used in [41] to reconstruct tree stem surface, but the technique requires several cameras.…”

Accuracy of Structure from Motion models in comparison with terrestrial laser scanner for the analysis of DBH and height influence on error behaviour

“…Based on the above, accuracy was not similar at the part of the stems for both point clouds. Also, according to Surový et al (2016), the fewer matching points on the stems from the same image indicate partially the inability of the photo camera to reconstruct more points especially at the higher parts of the tree stem and that is why error mostly greater than 11 cm was concentrated on tree stems and not on the points near and on the ground. Moreover, based on the histogram of Fig.…”

“…One of the advantages when using a hand-held camera is the ability to regulate the amount of shots to fully cover a tree structure in terms of elevation. However, according to Surový et al (2016), when they tried to examine the trend between height, azimuth and the error of reconstruction, there was a higher error in the areas of lower visibility (upper and lower parts of the stem). Point cloud generation based on MVS and image matching can fill gaps that are produced by TLS.…”