Results given by ST_Simplify inconsistent between PostGIS 1.5.2 and 2.0.1
|Reported by:||ChrisInCambo||Owned by:||pramsey|
I've recently upgraded to 2.0.1 and have noticed some inconsistencies between the both version in the behaviour of ST_Simplify.
If you run the statement from the docs:
SELECT ST_Npoints(the_geom) As np_before, ST_NPoints(ST_Simplify(the_geom,0.1)) As np01_notbadcircle, ST_NPoints(ST_Simplify(the_geom,0.5)) As np05_notquitecircle, ST_NPoints(ST_Simplify(the_geom,1)) As np1_octagon, ST_NPoints(ST_Simplify(the_geom,10)) As np10_triangle, (ST_Simplify(the_geom,100) is null) As np100_geometrygoesaway FROM (SELECT ST_Buffer('POINT(1 3)', 10,12) As the_geom) As foo;
Both return the same results for each column except "np100_geometrygoesaway", with 1.5.2 returning true as expected and 2.0.1 returning false.
When I use this method using real world data the differences are massive. For example the feature that I've tested on was 2120 points before simplification, then gets reduced to 7 when using a threshold of 0.1 on version 1.5.2, but for version 2.0.1 it only gets reduced to 2110.