| 33 | | 1) '''ST_AsRaster''' takes a geometry and converts it to a raster. |
| 34 | | |
| 35 | | 2) '''ST_Interpolate''' should be an aggregate taking a set of points (e.g. filtered lidar points) or line geometries (e.g. digitized topo lines) and their associated values and returning a raster representing a surface interpolated from those values. There are numerous methods of [http://en.wikipedia.org/wiki/Interpolation interpolation] and it would nice to have a generic method so we can use all of them, but we’re first targeting [http://en.wikipedia.org/wiki/Bilinear_interpolation bilinear interpolation], which will fill most needs and lay the ground for other methods. For reference, you might want to check an implementation in [http://apps.nrbook.com/empanel/index.html Numerical Recipes (chap. 3)] or in [http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Interpolation/Chapter_main.html#Section_68.3 CGAL]. Converting a point table to a TIN and then to a raster is also a way to go. A Delaunay triangulation can be produced with the [http://www.cs.cmu.edu/~quake/triangle.html Triangle library] (copyright issues should be checked first). See also [http://postgis.17.n6.nabble.com/Voronoi-Dalaunay-function-again-td3522575.html here] and [http://postgis.17.n6.nabble.com/Voronoi-tessellation-td4549913.html here]. |
| | 33 | 1) '''ST_Interpolate''' should be an aggregate taking a set of points (e.g. filtered lidar points) or line geometries (e.g. digitized topo lines) and their associated values and returning a raster representing a surface interpolated from those values. There are numerous methods of [http://en.wikipedia.org/wiki/Interpolation interpolation] and it would nice to have a generic method so we can use all of them, but we’re first targeting [http://en.wikipedia.org/wiki/Bilinear_interpolation bilinear interpolation], which will fill most needs and lay the ground for other methods. For reference, you might want to check an implementation in [http://apps.nrbook.com/empanel/index.html Numerical Recipes (chap. 3)] or in [http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Interpolation/Chapter_main.html#Section_68.3 CGAL]. Converting a point table to a TIN and then to a raster is also a way to go. A Delaunay triangulation can be produced with the [http://www.cs.cmu.edu/~quake/triangle.html Triangle library] (copyright issues should be checked first). See also [http://postgis.17.n6.nabble.com/Voronoi-Dalaunay-function-again-td3522575.html here] and [http://postgis.17.n6.nabble.com/Voronoi-tessellation-td4549913.html here]. |
