Description

Forces a geometry to use the geometry types defined by the requested version of the OGC Simple Features Specification. The default is SFS 1.1. Curved geometries are converted to linear representations, TRIANGLE is converted to POLYGON, and TIN and POLYHEDRALSURFACE are converted to GEOMETRYCOLLECTION values containing POLYGON elements.

If version begins with 1.2, curved geometries are still converted to linear representations, but TRIANGLE, TIN, and POLYHEDRALSURFACE are preserved. Other version values use the default SFS 1.1 behavior. Geometry collections are processed recursively, and the SRID and Z/M coordinates are preserved.

Availability: 2.1.0

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This method supports Circular Strings and Curves.

This function supports 3d and will not drop the z-index.

Examples

Compare the geometry types produced for SFS 1.1 (the default) and SFS 1.2. Read each row from the input type in the direction of the result columns.

WITH inputs(geom) AS (VALUES
    ('CIRCULARSTRING(0 0, 1 1, 2 0)'::geometry),
    ('TRIANGLE((0 0, 0 2, 2 0, 0 0))'::geometry),
    ('TIN(((0 0, 0 2, 2 0, 0 0)))'::geometry),
    ('POLYHEDRALSURFACE(((0 0, 0 2, 2 0, 0 0)))'::geometry)
)
SELECT ST_GeometryType(geom) || ' →' AS input,
       ST_GeometryType(ST_ForceSFS(geom)) AS "SFS 1.1 (default)",
       ST_GeometryType(ST_ForceSFS(geom, '1.2')) AS "SFS 1.2"
FROM inputs;

         input          |   SFS 1.1 (default)   |       SFS 1.2
------------------------+-----------------------+----------------------
 ST_CircularString →    | ST_LineString         | ST_LineString
 ST_Triangle →          | ST_Polygon            | ST_Triangle
 ST_Tin →               | ST_GeometryCollection | ST_Tin
 ST_PolyhedralSurface → | ST_GeometryCollection | ST_PolyhedralSurface
(4 rows)

See Also

ST_CurveToLine, ST_ForceCurve