ST_SIMPLIFY()

All functions > GEOSPATIAL > ST_SIMPLIFY()

Returns a simplified version of a geometry using the Douglas Peucker algorithm.

Signatures

Simplify

Returns: Simplified geometry, same sub kind as input

ST_SIMPLIFY(geo: T, tolerance: DOUBLE) → GEOMETRY or GEOGRAPHY

With:

• T : Custom types: GEOM_POINT | GEOM_LINESTRING | GEOM_POLYGON | GEOM_MULTIPOINT | GEOM_MULTILINESTRING | GEOM_MULTIPOLYGON | GEOM_MULTIANY | GEOG_POINT | GEOG_LINESTRING | GEOG_POLYGON | GEOG_MULTIPOINT | GEOG_MULTILINESTRING | GEOG_MULTIPOLYGON | GEOG_MULTIANY

Signature notes:

• Uses the Douglas Peucker algorithm to reduce vertex count
• On GEOMETRY: tolerance is in SRID coordinate units
• On GEOGRAPHY: tolerance is in meters (BigQuery) or degrees (DuckDB, depending on engine)
• Points are returned unchanged
• On Trino: transpiled to simplify_geometry()
• Returns NULL if any input is NULL

Examples

SELECT
    f1 := ST_ASTEXT(ST_SIMPLIFY(ST_GEOMFROMTEXT('LINESTRING (0 0, 1 1, 2 0, 3 1, 4 0)'), 1.5)) -- Simplify a zigzag line with high tolerance
;