ST_ReducePrecision — Returns a valid geometry with points rounded to a grid tolerance.
geometry ST_ReducePrecision(geometry
g, float8
gridsize);
Returns a valid geometry with all points rounded to the provided grid tolerance, and features below the tolerance removed.
Unlike ST_SnapToGrid the returned geometry will be valid, with no ring self-intersections or collapsed components.
Precision reduction can be used to:
match coordinate precision to the data accuracy
reduce the number of coordinates needed to represent a geometry
ensure valid geometry output to formats which use lower precision (e.g. text formats such as WKT, GeoJSON or KML when the number of output decimal places is limited).
export valid geometry to systems which use lower or limited precision (e.g. SDE, Oracle tolerance value)
Availability: 3.1.0 - requires GEOS >= 3.9.0.
SELECT ST_AsText(ST_ReducePrecision('POINT(1.412 19.323)', 0.1));
st_astext
-----------------
POINT(1.4 19.3)
SELECT ST_AsText(ST_ReducePrecision('POINT(1.412 19.323)', 1.0));
st_astext
-------------
POINT(1 19)
SELECT ST_AsText(ST_ReducePrecision('POINT(1.412 19.323)', 10));
st_astext
-------------
POINT(0 20)
Precision reduction can reduce number of vertices
SELECT ST_AsText(ST_ReducePrecision('LINESTRING (10 10, 19.6 30.1, 20 30, 20.3 30, 40 40)', 1));
st_astext
-------------
LINESTRING (10 10, 20 30, 40 40)
Precision reduction splits polygons if needed to ensure validity
SELECT ST_AsText(ST_ReducePrecision('POLYGON ((10 10, 60 60.1, 70 30, 40 40, 50 10, 10 10))', 10));
st_astext
-------------
MULTIPOLYGON (((60 60, 70 30, 40 40, 60 60)), ((40 40, 50 10, 10 10, 40 40)))