K. Streicher (2022)

Digital Surveying of Large-Scale Multi-Layered Terrain

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Master's Thesis (TU Wien)


Geomorphometry is the science of quantitative analysis of terrain surfaces. By surveying terrains to quantify their surfaces, it is possible to calculate the geomorphometric properties, such as heights, curvature, slopes, and distances. These are important for the analysis of terrains in archaeology, geology, planetary sciences, and others. By using digital terrain reconstructions, off-site terrain surveying becomes possible. The high resolution or large scale of terrains are a challenge for real-time rendering at interactive frame rates for exploration. This requires limiting resolution or loading smaller terrain parts. The use of terrain streaming allows rendering higher resolution or terrains of greater extents. As errors remain, it is important to quantify and visualize them. In this thesis, an out-of-core rendering algorithm for large-scale multi-layered terrain is presented. The presented streaming algorithm manages to stream scenes with 775 M triangles and 156 GB on their finest LOD, and a total size of 222 GB, at interactive frame-rates and on commodity hardware. Additionally, an improved measurement algorithm for digital terrain surveying of largescale multi-layered terrain is presented in this thesis. The measurement algorithm using variable-rate subsampling (VRSS) and Shared Edge Detection (SED), is called VRSS+SED and achieves better results than the fixed-rate subsampling (FRSS) strategy used in state-of-the-art planetary geology tools such as Planetry Robotics 3D Viewer (PRo3D). It achieves earlier termination at higher precision for the same number of samples by intersecting found shared edges with the ray casting plane to analytically calculate the midpoint between two neighboring primitives. Furthermore, a novel uncertainty metric called On-Data Ratio (ODR) is presented which allows raising awareness about the uncertainty in the results of the used state-of-the-art measurements algorithm. The presented algorithms are evaluated using an implementation in a prototype using the Unity engine and its Data-Oriented Techstack (DOTS). The algorithms are evaluted against PRo3D and the results are presented and discussed. The presented implementation achieves 15x as fast loading times as Pro3D for the 222 GB large scene at a similar storage size.