The photogrammetry example would be incomplete if we did not produce a digital terrain model from our inputs. A fully rigorous solution where the input point cloud would be classified into ground points, building points, and vegetation points is not feasible here, but this recipe will provide the basic framework for accomplishing such a solution.

In this recipe, we will create a 3D TIN, which will represent the surface of the point cloud.

WITH tin AS
(
  SELECT ST_DelaunayTriangles(ST_Union(the_geom), 0.0, 2) AS the_geom FROM
  chp07.uas
)
SELECT the_geom FROM tin;