University of Twente Student Theses
Automatic 3D modeling of train rails in a lidar point cloud
Benito, Daniel Díaz (2012) Automatic 3D modeling of train rails in a lidar point cloud.
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| Abstract: | Rail track irregularities have a large effect on railway safety and operation. To ensure a good maintenance of the rails, frequent measurements are needed, which are costly and require specific tools for different aspects of the rails geometry. Laser scanning offers the advantage of acquiring accurate 3D measurements of all the objects present in the railway environment in a short operational time. While some work has been done to detect the presence of rails and other objects in the point cloud, the modelling of those objects has received little attention. Such models not only enable all sorts of measurements about the rail geometry, but also facilitate simulations in train research. The purpose of this thesis is to develop a method to automatically build a 3D model of train rails from a point cloud where the rails have been already detected. First of all, the rail point cloud is sectioned into pieces of equal length. The points laying in each of the planes of the head of the rail are then identified. A non-linear least squares adjustment is used to find the parameters of the model pieces that best fit into the point cloud by minimizing the distance from the points to their corresponding planes. Finally, the model pieces are adjusted globally using a 6 dimensional non-rational Bezier curve, which yields a set of rail profiles that can be connected to build the final model representing the curved shape of the rail. The final model is validated by computing the distance from each point in the point cloud to the end model. The results showed that 90% of the points were at less than 1 cm distance to the reconstructed model, while the mean distance is 0.5 cm and 95% of the points were at less than 1.4 cm. Although the results are dependent on the accuracy of acquisition and detection methods, the overall performance of the method demonstrates that it is possible to model the train rails accurately by surface fitting and curvature adjustment. |
| Item Type: | Essay (Master) |
| Faculty: | ITC: Faculty of Geo-information Science and Earth Observation |
| Programme: | Geoinformation Science and Earth Observation MSc (75014) |
| Link to this item: | https://purl.utwente.nl/essays/93580 |
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