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ST_PERIMETER¶
Returns the geodesic length in meters of the perimeter of the polygon(s) in a GEOGRAPHY object.
Syntax¶
ST_PERIMETER( <geography_expression> )
Arguments¶
geography_expression
The argument must be of type GEOGRAPHY.
Returns¶
Returns a REAL value, which represents the length in meters.
Usage Notes¶
If
geography_expression
is not a Polygon, MultiPolygon, or GeometryCollection containing polygons, ST_PERIMETER returns 0.If
geography_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¶
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 | +------------------------------------------------------------------+