ST_MinimumBoundingRadius — Returns the center point and radius of the smallest circle that contains a geometry.
(geometry, double precision) ST_MinimumBoundingRadius(geometry geom);
Computes the center point and radius of the smallest circle that contains a geometry. Returns a record with fields:
center - center point of the circle
radius - radius of the circle
Use with ST_Collect to get the minimum bounding circle of a set of geometries.
To compute two points lying on the minimum circle (the "maximum diameter") use ST_LongestLine.
Availability - 2.3.0
SELECT ST_AsText(center), radius FROM ST_MinimumBoundingRadius('POLYGON((26426 65078,26531 65242,26075 65136,26096 65427,26426 65078))');
st_astext | radius
------------------------------------------+------------------
POINT(26284.8418027133 65267.1145090825) | 247.436045591407