- M. Disney (1)
- T. Fourcaud (1)
- B. Gardiner (1)
- M. Herold (1)
- T. Jackson (1)
- Philippe Lejeune (1)
- Y. Malhi (1)
- N. Origo (1)
- P. Raumonen (1)
- A. Shenkin (1)
- A. Wellpott (1)
Finite element analysis of trees in the wind based on terrestrial laser scanning data
Jackson, T. ; Shenkin, A. ; Wellpott, A. ; Calders, K. ; Origo, N. ; Disney, M. ; Burt, A. ; Raumonen, P. ; Gardiner, B. ; Herold, M. ; Fourcaud, T. ; Malhi, Y. - \ 2019
Agricultural and Forest Meteorology 265 (2019). - ISSN 0168-1923 - p. 137 - 144.
Critical wind speed - Finite element analysis - Resonant frequency - Terrestrial laser scanning - TLS - Wind damage
Wind damage is an important driver of forest structure and dynamics, but it is poorly understood in natural broadleaf forests. This paper presents a new approach in the study of wind damage: combining terrestrial laser scanning (TLS) data and finite element analysis. Recent advances in tree reconstruction from TLS data allowed us to accurately represent the 3D geometry of a tree in a mechanical simulation, without the need for arduous manual mapping or simplifying assumptions about tree shape. We used this simulation to predict the mechanical strains produced on the trunks of 21 trees in Wytham Woods, UK, and validated it using strain data measured on these same trees. For a subset of five trees near the anemometer, the model predicted a five-minute time-series of strain with a mean cross-correlation coefficient of 0.71, when forced by the locally measured wind speed data. Additionally, the maximum strain associated with a 5 ms−1 or 15 ms-1 wind speed was well predicted by the model (N = 17, R2 = 0.81 and R2 = 0.79, respectively). We also predicted the critical wind speed at which the trees will break from both the field data and models and find a good overall agreement (N = 17, R2 = 0.40). Finally, the model predicted the correct trend in the fundamental frequencies of the trees (N = 20, R2 = 0.38) although there was a systematic underprediction, possibly due to the simplified treatment of material properties in the model. The current approach relies on local wind data, so must be combined with wind flow modelling to be applicable at the landscape-scale or over complex terrain. This approach is applicable at the plot level and could also be applied to open-grown trees, such as in cities or parks.
Forest inventory with terrestrial LiDAR : A comparison of static and hand-held mobile laser scanning
Bauwens, Sébastien ; Bartholomeus, Harm ; Calders, Kim ; Lejeune, Philippe - \ 2016
Forests 7 (2016)6. - ISSN 1999-4907
Digital elevation model - Forestry - Hand-held mobile laser scanning - HMLS - SLAM - Stem mapping - Terrestrial laser scanning - TLS
The application of static terrestrial laser scanning (TLS) in forest inventories is becoming more effective. Nevertheless, the occlusion effect is still limiting the processing efficiency to extract forest attributes. The use of a mobile laser scanner (MLS) would reduce this occlusion. In this study, we assessed and compared a hand-held mobile laser scanner (HMLS) with two TLS approaches (single scan: SS, and multi scan: MS) for the estimation of several forest parameters in a wide range of forest types and structures. We found that SS is competitive to extract the ground surface of forest plots, while MS gives the best result to describe the upper part of the canopy. The whole cross-section at 1.3 m height is scanned for 91% of the trees (DBH > 10 cm) with the HMLS leading to the best results for DBH estimates (bias of -0.08 cm and RMSE of 1.11 cm), compared to no fully-scanned trees for SS and 42% fully-scanned trees for MS. Irregularities, such as bark roughness and non-circular cross-section may explain the negative bias encountered for all of the scanning approaches. The success of using MLS in forests will allow for 3D structure acquisition on a larger scale and in a time-efficient manner.