public class ST_SimplifyVW
extends GenericUDF
Generates a new ST_Geometry object by simplifying the input geometry using the Visvalingham-Whyatt algorithm.
Format:
ST_SimplifyVW(geometry ST_Geometry, threshold NUMBER) - return a new ST_Geometry object by simplifying the input geometry using the Visvalingham-Whyatt Algorithm
This method takes a threshold as the input.
The threshold value to be used for the geometry simplification has to be expressed as a percentage value between 0 and 100.
As the value is decreased, the returned geometry is likely to be closer to the input geometry, as the value is increased then fewer points are likely to be in the returned geometry.
Example:
select ST_SimplifyVW(
ST_Polygon('{"type": "Polygon","coordinates": [[[1, 2], [1.01, 2.01], [5, 2], [5, 6], [1, 6], [1, 2]]]}', 8307)
, 50) from hivetable LIMIT 1; -- return {"type":"Polygon", "coordinates":[[[1,2],[5,6],[1,6],[1,2]]],"crs":{"type":"name","properties":{"name":"EPSG:8307"}}}