Categories:

Geospatial functions

ST_PERIMETER

Returns the length of the perimeter of the polygon(s) in a GEOGRAPHY or GEOMETRY object.

Syntax

ST_PERIMETER( <geography_or_geometry_expression> )

Arguments

geography_or_geometry_expression

The argument must be of type GEOGRAPHY or GEOMETRY.

Returns

Returns a REAL value, which represents the length:

  • For GEOGRAPHY objects, the length is in meters.
  • For GEOMETRY objects, the length is computed with the same unit used to define the coordinates.

Usage notes

  • If geography_or_geometry_expression is not a Polygon, MultiPolygon, or GeometryCollection containing Polygons, ST_PERIMETER returns 0.
  • If geography_or_geometry_expression is a GeometryCollection, ST_PERIMETER returns the sum of the perimeters of the Polygons in the collection.
  • Use this function (rather than ST_LENGTH) to get the perimeter of a Polygon.

Examples

GEOGRAPHY examples

This calculates the length of the perimeter of a polygon that is one degree of arc on each edge and has one edge on the equator:

SELECT ST_PERIMETER(TO_GEOGRAPHY('POLYGON((0 0, 1 0, 1 1, 0 1, 0 0))'));
+------------------------------------------------------------------+
| ST_PERIMETER(TO_GEOGRAPHY('POLYGON((0 0, 1 0, 1 1, 0 1, 0 0))')) |
|------------------------------------------------------------------|
|                                                 444763.468727621 |
+------------------------------------------------------------------+

GEOMETRY examples

The following example demonstrates how to use the ST_PERIMETER function.

SELECT ST_PERIMETER(g), ST_ASWKT(g)
FROM (SELECT TO_GEOMETRY(column1) AS g
  FROM VALUES ('POINT(1 1)'),
              ('LINESTRING(0 0, 1 1)'),
              ('POLYGON((0 0, 0 1, 1 1, 1 0, 0 0))'));
+-----------------+--------------------------------+
| ST_PERIMETER(G) | ST_ASWKT(G)                    |
|-----------------+--------------------------------|
|               0 | POINT(1 1)                     |
|               0 | LINESTRING(0 0,1 1)            |
|               4 | POLYGON((0 0,0 1,1 1,1 0,0 0)) |
+-----------------+--------------------------------+