PostGIS

ST_MaximumInscribedCircle
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ST_MaximumInscribedCircle

8.14. Geometry Processing

Name

ST_MaximumInscribedCircle — Computes the largest circle contained within a geometry.

Synopsis

(geometry, geometry, double precision) +`*`+ST_MaximumInscribedCircle*(`geometry `geom`)`;

Description

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

center - center point of the circle
nearest - a point on the geometry nearest to the center
radius - radius of the circle

For polygonal inputs, the circle is inscribed within the boundary rings, using the internal rings as boundaries. For linear and point inputs, the circle is inscribed within the convex hull of the input, using the input lines and points as further boundaries.

Availability: 3.1.0 - requires GEOS >= 3.9.0.

Examples

st_maximuminscribedcircle01

Maximum inscribed circle of a polygon. Center, nearest point, and radius are returned.

SELECT radius, ST_AsText(center) AS center, ST_AsText(nearest) AS nearest
    FROM ST_MaximumInscribedCircle(
        'POLYGON ((40 180, 110 160, 180 180, 180 120, 140 90, 160 40, 80 10, 70 40, 20 50, 40 180),
        (60 140, 50 90, 90 140, 60 140))');

     radius      |           center           |    nearest
-----------------+----------------------------+---------------
 45.165845650018 | POINT(96.953125 76.328125) | POINT(140 90)

st_maximuminscribedcircle02

Maximum inscribed circle of a multi-linestring. Center, nearest point, and radius are returned.