public class MinimumClearance extends Object
The Minimum Clearance is a measure of what magnitude of perturbation of the vertices of a geometry can be tolerated before the geometry becomes topologically invalid. The smaller the Minimum Clearance distance, the less vertex perturbation the geometry can tolerate before becoming invalid.
The concept was introduced by Thompson and Van Oosterom [TV06], based on earlier work by Milenkovic [Mi88].
The Minimum Clearance of a geometry G is defined to be the value r such that "the movement of all points by a distance of r in any direction will guarantee to leave the geometry valid" [TV06]. An equivalent constructive definition [Mi88] is that r is the largest value such:
If G is a
then in fact no amount of perturbation
will render the geometry invalid.
In this case a Minimum Clearance is still computed
based on the vertex and segment distances
according to the constructive definition.
It is possible for no Minimum Clearance to exist.
For instance, a
MultiPoint with all members identical
has no Minimum Clearance
(i.e. no amount of perturbation will cause
the member points to become non-identical).
Empty geometries also have no such distance.
The lack of a meaningful MinimumClearance distance is detected
and suitable values are returned by
The computation of Minimum Clearance utilizes
method to provide good performance even for
An interesting note is that for the case of
the computed Minimum Clearance line
effectively determines the Nearest Neighbours in the collection.
|Constructor and Description|
Creates an object to compute the Minimum Clearance for the given Geometry
|Modifier and Type||Method and Description|
Gets the Minimum Clearance distance.
Computes the Minimum Clearance distance for the given Geometry.
Gets a LineString containing two points which are at the Minimum Clearance distance.
Gets a LineString containing two points which are at the Minimum Clearance distance for the given Geometry.
public MinimumClearance(Geometry geom)
geom- the input geometry
public static double getDistance(Geometry g)
g- the input geometry
g- the input geometry
public double getDistance()
If no distance exists (e.g. in the case of two identical points) Double.MAX_VALUE is returned.
public LineString getLine()
If no distance could be found (e.g. in the case of two identical points) LINESTRING EMPTY is returned.
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