UAV photogrammetry in PostGIS – DSM creation

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.

Getting ready

Before we start, ST_DelaunayTriangles is available only in PostGIS 2.1 using GEOS 3.4. This is one of the few recipes in this book to require such advanced versions of PostGIS and GEOS.

How it works...

ST_DelaunayTriangles will calculate a 3D TIN with the correct flag: geometry ST_DelaunayTriangles (geometry g1, float tolerance, int4 flags).

CREATE TABLE chp07.uas_tin AS

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

Now...