![Sample our Geography journals, sign in here to start your FREE access for 14 days]({"type":"image" , "src" : "/sda/5937/TOC-Subject-Sample-2021-Geography.jpg"})
Abstract
For storing and modeling three-dimensional (3D) topographic objects (e.g. buildings, roads, dykes, and the terrain), tetrahedralizations have been proposed as an alternative to boundary representations. While in theory they have several advantages, current implementations are either not space efficient or do not store topological relationships (which makes spatial analysis and updating slow, or require the use of an expensive 3D spatial index). We discuss in this paper an alternative data structure for storing tetrahedralizations in a database management system (DBMS). It is based on the idea of storing only the vertices and stars of edges; triangles and tetrahedra are represented implicitly. It has been used previously in main memory, but not in a DBMS. We describe how to modify it to obtain an efficient implementation in a DBMS, and we describe how it can be used for modeling 3D topography. As we demonstrate with different real-world examples, the structure is compacter than known alternatives, it permits us to store attributes for any primitives, and has the added benefit of being topological, which permits us to query it efficiently. The structure can be easily implemented in most DBMS (we describe our implementation in PostgreSQL), and we present some of the engineering choices we made for the implementation.
Acknowledgments
This research is supported by the Dutch Technology Foundation STW, which is part of the Netherlands Organization for Scientific Research (NWO), and which is partly funded by the Ministry of Economic Affairs (project codes: 11300 and 11185).
Notes
1. Notice that this model is often called “TEN”, which stands for either TEtrahedral Network, TEtrahedral irregular Network, TEtrahedronized irregular Network, or TEtrahedron Network, depending on the authors. For the purpose of this paper, they are all equivalent and a TEN is a tetrahedralization, as defined in Section 2.