Class MaximumInscribedCircle

Hierarchy: Object , MaximumInscribedCircle

public class MaximumInscribedCircle

Constructs the Maximum Inscribed Circle for a polygonal Geometry, up to a specified tolerance. The Maximum Inscribed Circle is determined by a point in the interior of the area which has the farthest distance from the area boundary, along with a boundary point at that distance.

In the context of geography the center of the Maximum Inscribed Circle is known as the Pole of Inaccessibility. A cartographic use case is to determine a suitable point to place a map label within a polygon.

The radius length of the Maximum Inscribed Circle is a measure of how "narrow" a polygon is. It is the distance at which the negative buffer becomes empty.

The class supports polygons with holes and multipolygons.

The implementation uses a successive-approximation technique over a grid of square cells covering the area geometry. The grid is refined using a branch-and-bound algorithm. Point containment and distance are computed in a performant way by using spatial indexes.

Future Enhancements

Support a polygonal constraint on placement of center

Authors:: Martin Davis

public MaximumInscribedCircle(Geometry polygonal, double tolerance)

Creates a new instance of a Maximum Inscribed Circle computation.

Parameters:: polygonal - polygonal an areal geometry; tolerance - tolerance the distance tolerance for computing the centre point

public static Point getCenter(Geometry polygonal, double tolerance)

Computes the center point of the Maximum Inscribed Circle of a polygonal geometry, up to a given tolerance distance.

Parameters:: polygonal - polygonal a polygonal geometry; tolerance - tolerance the distance tolerance for computing the center point

Returns:: the center point of the maximum inscribed circle

public static LineString getRadiusLine(Geometry polygonal, double tolerance)

Computes a radius line of the Maximum Inscribed Circle of a polygonal geometry, up to a given tolerance distance.

Parameters:: polygonal - polygonal a polygonal geometry; tolerance - tolerance the distance tolerance for computing the center point

Returns:: a line from the center to a point on the circle

public Point getCenter()

Gets the center point of the maximum inscribed circle (up to the tolerance distance).

Returns:: the center point of the maximum inscribed circle

public Point getRadiusPoint()

Gets a point defining the radius of the Maximum Inscribed Circle. This is a point on the boundary which is nearest to the computed center of the Maximum Inscribed Circle. The line segment from the center to this point is a radius of the constructed circle, and this point lies on the boundary of the circle.

Returns:: a point defining the radius of the Maximum Inscribed Circle

public LineString getRadiusLine()

Gets a line representing a radius of the Largest Empty Circle.

Returns:: a line from the center of the circle to a point on the edge