Creating a TIN

To make a TIN, all you need is a set of input points; 3D Analyst makes the triangles.

Input points and the output TIN structure.

The input points must contain elevation information—either from an attribute in the layer attribute table or from z-values in the feature geometry.

The input data can be point features, or they can be the vertices of line or polygon features. TINs are often created from contour lines, for example.

Each triangle in the TIN is a plane and therefore has one slope value and one aspect value. Triangles have unique elevation values for every x,y coordinate location within them. Elevation is determined by interpolation from the node values of the triangle enclosing the location.

The TIN triangulation method

TIN triangles are created through Delaunay triangulation. An essential feature of this method is that a circle drawn through the three nodes of any triangle contains no other input point.

A circle drawn through the nodes of triangle DEG contains no other points. The same is true of every triangle in the TIN.

One advantage of Delaunay triangulation is that it makes triangles as equi-angular (or “fat”) as possible. This is good because long skinny triangles present computational problems. Another advantage is that the triangulation is the same regardless of the order in which the input points are processed.