Surface feature types

All you need to make a TIN is a set of points with elevation values. These points, which may come from point, line, or polygon features, are called “mass points” because they define the structure, or mass, of the TIN.

Real terrain, however, often has unique formations that are not well-modeled by mass point triangulation. Ridges, cliffs, gullies, and man-made grades are a few examples. To capture such formations, you can add line and polygon layers to the triangulation process.

For example, if your study area includes a lake, you probably want the surface to be flat where the lake is. You can add a lake polygon to the TIN that forces the surface to be flat. If your study area has hills, you can add ridge line features to the TIN to ensure that ridges are maintained.

A mass point triangulation (top) does not adequately model high-definition surface details, such as the graded building footprints of the improved model (bottom).

You make these refinements to the TIN structure by adding feature layers as particular surface feature types. In the next concepts, you will learn more about them. The chart below summarizes the surface feature types you can add to a TIN.

A summary of TIN surface feature types.