3D assessment of rockfall hazard and risk mitigation

How to manage large and oversampled DTMs in RocPro3D?



August 3rd, 2023

In order to run simulations with #RocPro3D, a Digital Terrain Model (DTM) is required. This DTM can be very large for high spatial resolution, which often leads to oversampling. In practice, RocPro3D can easily manage DTMs containing several hundred thousand faces. However, above a million faces, it may be advisable to reduce the mesh size to make the model easier to handle and to speed up the trajectory simulations.

This capability is built into RocPro3D through two decimation methods that allow the number of faces to be reduced while maintaining the topographic accuracy of the DTM.

Below is an illustration of the #decimation performed in RocPro3D, starting from an initial TRN* mesh (only partially shown) with ~1.22 million faces, based on a 0.5 m resolution raster. After decimation, the produced TIN** mesh is only ~0.24 million face. In this case the distance between the original and the decimated mesh is less than ±6cm, reflecting the very good approximation of the decimated mesh to the original mesh.

*TRN: Triangulated Regular Network; **TIN: Triangulated Irregular Network

Portion of the original TRN mesh (raster, 0.5m resolution) ~1.22 million faces
Portion of the decimated TIN mesh (83% ratio) ~0.24 million faces
Max error between meshes ± 6cm