Class DiscreteHausdorffDistance

An algorithm for computing a distance metric which is an approximation to the Hausdorff Distance based on a discretization of the input Geometry.

Inheritance

object

DiscreteHausdorffDistance

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: NetTopologySuite.Algorithm.Distance

Assembly: NetTopologySuite.dll

Syntax

public class DiscreteHausdorffDistance

Remarks

The algorithm computes the Hausdorff distance restricted to discrete points for one of the geometries. The points can be either the vertices of the geometries (the default), or the geometries with line segments densified by a given fraction. Also determines two points of the Geometries which are separated by the computed distance.

This algorithm is an approximation to the standard Hausdorff distance. Specifically,

for all geometries a, b:    DHD(a, b) <= HD(a, b)

The approximation can be made as close as needed by densifying the input geometries. In the limit, this value will approach the true Hausdorff distance:

DHD(A, B, densifyFactor) -> HD(A, B) as densifyFactor -> 0.0

The default approximation is exact or close enough for a large subset of useful cases.

Examples of these are:

computing distance between Linestrings that are roughly parallel to each other, and roughly equal in length. This occurs in matching linear networks.
Testing similarity of geometries.

An example where the default approximation is not close is:

A = LINESTRING (0 0, 100 0, 10 100, 10 100)
B = LINESTRING (0 100, 0 10, 80 10)
DHD(A, B) = 22.360679774997898
HD(A, B) ~= 47.8

Constructors

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DiscreteHausdorffDistance(Geometry, Geometry)

Creates an instance of this class using the provided geometries

Declaration

public DiscreteHausdorffDistance(Geometry g0, Geometry g1)

Parameters

Type	Name	Description
Geometry	g0	A geometry
Geometry	g1	Another geometry

Properties

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Coordinates

Gets a value indicating the

Declaration

public Coordinate[] Coordinates { get; }

Property Value

Type	Description
Coordinate[]

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DensifyFraction

Gets or sets the fraction by which to densify each segment.

Declaration

public double DensifyFraction { get; set; }

Property Value

Type	Description
double

Remarks

Each segment will be (virtually) split into a number of equal-length sub-segments, whose fraction of the total length is closest to the given fraction.

Methods

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Distance()

Computes the discrete hausdorff distance between the two assigned geometries.

Declaration

public double Distance()

Returns

Type	Description
double	The discrete hausdorff distance

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Distance(Geometry, Geometry)

Computes the Discrete Hausdorff Distance of two Geometrys.

Declaration

public static double Distance(Geometry g0, Geometry g1)

Parameters

Type	Name	Description
Geometry	g0	A geometry
Geometry	g1	A geometry

Returns

Type	Description
double	The Discrete Hausdorff Distance

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Distance(Geometry, Geometry, double)

Computes the Discrete Hausdorff Distance of two Geometrys.

Declaration

public static double Distance(Geometry g0, Geometry g1, double densifyFraction)

Parameters

Type	Name	Description
Geometry	g0	A geometry
Geometry	g1	A geometry
double	densifyFraction	The densify fraction. A value of 0 indicates, that no densification should take place

Returns

Type	Description
double	The Discrete Hausdorff Distance

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OrientedDistance()

Computes the discrete hausdorff distance between the 1st and the 2nd assigned geometry

Declaration

public double OrientedDistance()

Returns

Type	Description
double	The discrete hausdorff distance.