ST_MaximumInscribedCircle¶

Introduction: Finds the largest circle that is contained within a (multi)polygon, or which does not overlap any lines and points. Returns a row with fields:

ST_MaximumInscribedCircle

center - center point of the circle
nearest - nearest point from the center of the circle
radius - radius of the circle

For polygonal geometries, the function inscribes the circle within the boundary rings, treating internal rings as additional constraints. When processing linear and point inputs, the algorithm inscribes the circle within the convex hull of the input, utilizing the input lines and points as additional boundary constraints.

Formats:

ST_MaximumInscribedCircle(geometry: Geometry)
ST_MaximumInscribedCircle(geometry: Geometry, tolerance: Double)

The optional tolerance controls when the circle-center search stops refining. A value of 0 uses the geometry-dependent default max(width, height) / 1000, which is also used by the one-argument form. The tolerance must otherwise be positive. The two-argument overload was added in v1.9.1.

Return type: Struct<center: Geometry, nearest: Geometry, radius: Double>

Since: v1.6.1

SQL Example:

SELECT inscribedCircle.* FROM (
    SELECT ST_MaximumIncribedCircle(ST_GeomFromWKT('POLYGON ((62.11 19.68, 60.79 17.20, 61.30 15.96, 62.11 16.08, 65.93 16.95, 66.20 20.61, 63.08 21.43, 64.48 18.70, 62.11 19.68))')) AS inscribedCircle
)

Output:

+---------------------------------------------+-------------------------------------------+------------------+
|center                                       |nearest                                    |radius            |
+---------------------------------------------+-------------------------------------------+------------------+
|POINT (62.794975585937514 17.774780273437496)|POINT (63.36773534817729 19.15992378007859)|1.4988916836219184|
+---------------------------------------------+-------------------------------------------+------------------+