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> ) 

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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 | +------------------------------------------------------------------+ 

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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))')); 

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+-----------------+--------------------------------+ | 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)) | +-----------------+--------------------------------+ 

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