What is a DTM?
A Digital Terrain Model, DTM, is a collection of georeferenced plane segments, commonly with three distinct points forming a triangle. These triangles represent the shape of the Earth over some finite area.
The shape represented may be either the existing ground or a designed surface representing some kind of development project.
Adjoining triangles must share common vertices and triangle edges. The triangles must form a continuous, non-overlapping surface. Each possible 2D coordinate must be either a triangle vertex, a point of a triangle edge or be uniquely in a single triangle.
Example
This is an example of a DTM viewed from the 0,0,1 perspective in AutoCAD
The same DTM viewed from a different perspective
