ST_LongestLine — Returns the 2D longest line between two geometries.
geometry ST_LongestLine(geometry
g);
geometry ST_LongestLine(geometry
g1, geometry
g2);
Returns the 2-dimensional longest line between the points of two geometries.
The line returned starts on g1 and ends on g2.
The longest line always occurs between two vertices. The function returns the first longest line if more than one is found. The length of the line is equal to the distance returned by ST_MaxDistance.
If only one geometry is provided, or g1 and g2 are the same geometry, returns the line between the two vertices farthest apart in the geometry. The endpoints of the line lie on the circle computed by ST_MinimumBoundingCircle.
Availability: 1.5.0
Enhanced: 3.7.0 - support for a single geometry input.
Longest line between a Point and a LineString.
SELECT ST_LongestLine(
'POINT (160 40)',
'LINESTRING (10 30,50 50,30 110,70 90,180 140,130 190)' ) AS lline;
LINESTRING(160 40,130 190)
Longest line between two polygons.
SELECT ST_LongestLine(
'POLYGON ((190 150,20 10,160 70,190 150))',
ST_Buffer('POINT(80 160)', 30)
) AS llinewkt;
LINESTRING(20 10,91.4805029709527 187.7163859753386)
Longest line across a single geometry. The length of the line is equal to the Maximum Distance. The endpoints of the line lie on the Minimum Bounding Circle.
SELECT ST_LongestLine(geom) AS llinewkt,
ST_MaxDistance(geom) AS max_dist,
ST_Length(ST_LongestLine(geom)) AS lenll
FROM (SELECT 'POLYGON ((40 180,110 160,180 180,180 120,140 90,160 40,80 10,70 40,20 50,40 180),
(60 140,99 77.5,90 140,60 140))'::geometry AS geom) AS t;
llinewkt | max_dist | lenll ---------------------------+--------------------+-------------------- LINESTRING(20 50,180 180) | 206.15528128088303 | 206.15528128088303