Abstract
Trees play an important role in the complex system of urban environments. Their benefits to environment and health are manifold. Yet, especially near streets, the traffic can be impaired by a limited clearance. Even injuries could be caused by breaking tree parts. Hence, it is important to capture the trees in the frame of a tree cadastre and to ensure regular monitoring. Mobile laser scanning (MLS) can be used for data acquisition, followed by an automated analysis of the point clouds acquired over time. The presented approach uses occupancy grids with a grid size of 10 cm, which enable the comparison of several epochs in three-dimensional space. Prior to that, a segmentation of single tree objects is conducted. After cylinder-based trunk localisation, closely neighboured tree crowns are separated using weights derived from local point densities. Therefore, changes for every single tree can be derived with regard to its parameters and its point cloud. The testing area is set along an urban street in Munich, Germany, using the publicly available benchmark data sets TUM-MLS-2016/2018. In the frame of the evaluation, tree objects are geo-referenced and mapped in 2D. The tree parameters height and diameter at breast height are derived. The geometric evaluation of the change analysis facilitates not only the acquisition of stock changes, but also the detection of shape changes for the tree objects.
Highlights
Living in a technically advanced society like ours, the impression of an increasing segregation of human life and natural environment is not far to seek
We examine mobile laser scanning data sets from 2016 and 2018, both acquired by the same platform
Point cloud extractions based on change/no change will be used in detailed analysis and to show interesting properties of changing elements
Summary
Living in a technically advanced society like ours, the impression of an increasing segregation of human life and natural environment is not far to seek. Our everyday life, even as the inhabitant of a megacity, cannot be imagined without a living, natural environment to some degree In urbanised areas, this is often visible by large parks and single dominant trees along roads and in gardens. This is often visible by large parks and single dominant trees along roads and in gardens These trees have a considerable significance in a populated city (Nowak et al 2006; Armson et al 2013). People—afoot or by bike—cars, trucks, buildings, infrastructural installations, and the mentioned natural elements have to find a good way of coexistence This means that trees, as the possibly tallest plants in a city, must not endanger persons or other objects in case branches break down or the whole tree falls. The irregular shape of plants is a challenge to any automated processing
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