Contouring and Surface Interpolation

Contouring
1. Generate contours from evenly-spaced weighted points
2. Contouring Irregularly spaced points
Surface Interpolation
1. IDW Interpolation over a grid of points
2. Compute Z value of a TIN at a Point
  1. PostGIS TO DO - Add ST_3DInterpolate ?

Contouring

Generate contours from evenly-spaced weighted points

https://gis.stackexchange.com/questions/85968/clustering-points-in-postgresql-to-create-contour-map NO SOLUTION

Contouring Irregularly spaced points

https://abelvm.github.io/sql/contour/

Solution An impressive PostGIS-only solution using a Delaunay with triangles cut by contour lines. Uses the so-called Meandering Triangles method for isolines.

Surface Interpolation

IDW Interpolation over a grid of points

https://gis.stackexchange.com/questions/373153/spatial-interpolation-in-postgis-without-outputting-raster

Use Inverse-Distance-Weighting (IDW) interpolation on a subset of nearby points. The power parameter POWER is chosen according to the weighting desired..

SELECT SUM( z/d ) / SUM( 1/d ) AS z
FROM (
  SELECT smpl.z as z,
         ST_Distance(itp.geom, smpl.geom) ^ POWER AS d
  FROM   <point> AS smpl
  ORDER BY
         itp.geom <-> smpl.geom
  WHERE  smpl.Z IS NOT NULL
  LIMIT  <sample_size>
) t;

Compute Z value of a TIN at a Point

https://gis.stackexchange.com/questions/237506/query-z-at-intersecting-point-locations-from-a-multipolygonz

Solution

Use ST_3DIntersection (code here - requires SF_CGAL)
Use a custom function (code here)