ST_ConvexHull

Introduction: Returns the smallest convex region containing A. For Geometry inputs, the hull is computed in the coordinate plane. For Geography inputs, it is computed on the sphere and its edges follow geodesics.

Format:

ST_ConvexHull (A: Geometry)

ST_ConvexHull (A: Geography)

Return type: Geometry or Geography, matching the input type

Since: v1.0.0 (Geometry), v1.9.1 (Geography)

For a Geography input, a single unique point produces a Point, while collinear points produce a LineString. Empty inputs preserve their input type. Polygon holes do not change the hull. If the spherical convex hull is the full sphere, the function throws an UnsupportedOperationException because the full sphere cannot be represented by OGC WKB.

SQL Example

SELECT ST_ConvexHull(ST_GeomFromText('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))'))

Output:

POLYGON ((20 40, 175 150, 125 100, 20 40))

Geography SQL Example

SELECT ST_GeometryType(
    ST_ConvexHull(
        ST_GeogFromWKT(
            'MULTIPOINT ((170 -10), (170 10), (-170 10), (-170 -10))',
            4326
        )
    )
)

Output:

ST_Polygon