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Raumonen, Pasi Empirical 3D and 4D structural tree models from TLS data Keynote Downloadable
Pasi Raumonen1, Markku Åkerblom1 and Mikko Kaasalainen1
(1) Tampere University, Finland

Terrestrial laser scanning (TLS) can be used to accurately and non-destructively measure trees. Good-quality TLS data samples the detailed 3D structure of the woody parts into a 3D point cloud. From the data we can reconstruct a quantitative structure model (QSM) of the 3D woody structure of a tree. An empirical or data-based QSM consists of a hierarchical collection of cylinders, or other geometric primitives, fitted to the TLS data. The surface and volume of the stem and each individual branch are thus reconstructed with a collection of consecutive cylinders. QSMs also contain other geometric information, such as height and length of the branches and branching angles. Moreover, the topological branching structure --branching order and parent-child relation of the branches-- is also recorded in the QSMs. The reconstruction of QSMs, in general, do not employ biological growth rules or follow the actual growth patterns, except perhaps enforcing tapering of the branch diameter. Thus, in general, the elements (cylinders) of QSMs do not correspond to botanical or architectural elements of the tree, e.g. annual growth in length. Similarly, the elements do not contain information if the branch is alive or dead or about the foliage. However, there are methods that allow to estimate the location, area and angles of the leaves from the TLS data, and this information can be added to the QSM elements. Repeating TLS measurements annually will produce a time series of the 3D woody structure which can be regarded as a kind of empirical 4D tree model.