A Word About DTMs and TINS

Seems I have gotten ahead of myself, I have started posting about things like DTMs and TINs and I have not attempted to explain what they are. For starters, a DTM is a Digital Terrain Model and a TIN is a Triangulated Irregular Network. For the most part, I often use the terms interchangeably but there is a minute difference. Both terms represent a surface, a composition of plane segments that represent and model the shape of the earth. Both compositions contain points, connected by line segments, line segments that define edges of triangles. Adjoining triangles share both vertices and edges; the vertex of one triangle cannot lie in the interior of another triangle.

The difference lies in the orientation of the points; a DTM is most often affiliated with designed surfaces while a TIN is often associated with field collected data, hence the irregular-ness.

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2 Responses to A Word About DTMs and TINS

  1. Ian Lilly says:

    I’d clarify your definitions a little more.
    My understanding is that a DTM is typically made up of data that represents a terrain surface. It might be gridded data (eg least squares, min curvature, etc or simply closely spaced observed data – eg LIDAR or laser ranging). A DTM can also be a TIN but a it’s not necessary.
    A TIN is a triangulated surface but has special characteristics. It has “break lines” which are typically breaks in slope which triangles DO NOT CROSS. Examples are ridge lines, streams, curbs, geological fault lines, escarpments etc.
    Typical programs to generate DTM are gridding programs or triangulation programs (eg TRIANGLE or ACORD by Schewchuk or Watson resp) and are a Delaunay triangulation. TINs are typically NOT Delaunay.

  2. Dave says:

    I appreciate your clarifications and you will get no argument from me. The brief articles hosted here were meant to give someone unfimilar with machine control a “knocking around knowledge” and being so I took some liberties with certain explinations.

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