Triangulated irregular network

A Triangulated Irregular Network (English triangulated irregular network, TIN ) is a way to model surfaces based on a 3D point cloud ( mass points).

TINs are used for the digital representation of the terrain, eg in geographic information systems.

In order to obtain a surface mass points to triangulated, thus creating a network structure: Triangulation of these parts of the model edges are created and limited by the edges of triangles with an area filling provided ( linear interpolation ). Since the triangulation of a point set P is not unique ( for P e R with P> 3), Triangulationskriterien are required. An important criterion is the so-called Delaunay triangulation.

The generated surfaces pass through clearly defined points, as there will be no loss of accuracy by interpolation and can be represented exactly, for example, breaklines in the field.

Since it is flat triangles, comes with a corresponding size " edgy " terrain representation about. Since the distribution of mass points can be irregular, however, areas with high relief energy can be precisely modeled and introduced subsequently points by increasing the dot density. The clear point definition of each point can only assume a height value, which excludes negative gradient (2.5 - D representation).

Storage

There are two different ways to save a TIN:

Surfaces
Node

Surfaces

Each triangle is marked with a unique key (ID). When saving an area adjacent areas are backed up. These two tables are created. A triangular table includes the ID of the triangle, the nodes forming the triangle, and the IDs of the adjacent triangles. A Node table containing the IDs of the nodes and their coordinates (x, y, z).

This form of storage is beneficial in area-based analyzes ( slope angle, surface runoff ).

Node

There is only one table. In which the node name, the coordinates (x, y, z) and the neighboring nodes are stored. The edge structure so it is stored.

This storage is applied to contour lines or creating terrain profiles.