![]() more points) can be used where the surface is complex (Figure 2A), and larger triangles (i.e. It is not sensitive to varying data scales, meaning that smaller triangles (i.e.The main advantages of the TIN model are as follows: LiDAR point cloud and raster data were directly obtained from U.S. TIN derived from the point cloud shown in A. An illustration of different ways of representing the same continuous surface at the same scale and extent. In this data structure, each point is connected by non-overlapping lines (edges) to create planes of contiguous triangles of varied sizes (hence the name irregular).įigure 1. Typically, the triangulation of a point cloud (x, y, z data) or grids serve as the basis for generating TINs. Introduced in the 1970s (Peucker et al., 1976), the surface is made up of adjacent, non-overlapping triangles. ![]() Alternatively, continuous surfaces may be represented by a grid in the raster format, where each cell represents one value (Figure 1C).Īnother way of representing a continuous surface is by applying a Triangular Irregular Network (TIN) (Figure 1D). elevation values) can be stored in vector form as either points with coordinate pairs (Figure 1A), or contours where nodes that make up these lines are stored as coordinate pairs (Figure 1B). There are different ways of representing continuous surfaces in a GIS environment. Any point in each polygon is close to its generating point than any other. Voronoi diagram: A partition of a plane into polygons such that each polygon has only one generating point. This may be stored in a raster or vector format.Ĭircumcircle (of a triangle): A circle passing through all the nodes of the triangle.ĭelaunay triangulation: A triangulation method which ensures that no point lies within the circumcircle of any triangles in the network These are the vertices of the triangles in a TIN.Ĭontours: Lines that connect points of equal elevation. Nodes: Points representing a sampled elevation value. Instead, the TIN data would usually be converted to other suitable formats.Īspect: Azimuthal direction of sloping facet However, the unique way of storing data an a TIN often makes it difficult to combine with other spatial data formats. TINs also have a high modelling potential, e.g. In other words, a TIN can be more detailed where the surface is complex (high variation) by using smaller facets, and less detailed where the surface is more homogeneous by using larger facets. TINs are efficient when storing heterogeneous surfaces, since homogenous areas are stored using few data points, while areas with more variability are stored in detail using a larger number of data points. Collectively, these hypothetical lines form a network covering the whole surface. These facets are planes that have the same slope and aspect over the facet. It is vector based, and works in such a way that it connects known data points with straight lines to create triangles, often called facets. A Triangular Irregular Network (TIN) is a way of storing continuous surfaces.
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