Class LineSequencer

Builds a sequence from a set of LineStrings, so that they are ordered end to end. A sequence is a complete non-repeating list of the linear components of the input. Each linestring is oriented so that identical endpoints are adjacent in the list.

The input linestrings may form one or more connected sets. The input linestrings should be correctly noded, or the results may not be what is expected. The output of this method is a single MultiLineString, containing the ordered linestrings in the sequence.

The sequencing employs the classic 'Eulerian path' graph algorithm. Since Eulerian paths are not uniquely determined, further rules are used to make the computed sequence preserve as much as possible of the input ordering. Within a connected subset of lines, the ordering rules are: - If there is degree-1 node which is the start node of an linestring, use that node as the start of the sequence. - If there is a degree-1 node which is the end node of an linestring, use that node as the end of the sequence. - If the sequence has no degree-1 nodes, use any node as the start

Not all arrangements of lines can be sequenced. For a connected set of edges in a graph, Euler's Theorem states that there is a sequence containing each edge once if and only if there are no more than 2 nodes of odd degree. If it is not possible to find a sequence, the IsSequenceable() property will return false.

Inheritance

Object

LineSequencer

Inherited Members

Object.Equals(Object)

Object.Equals(Object, Object)

Object.GetHashCode()

Object.GetType()

Object.MemberwiseClone()

Object.ReferenceEquals(Object, Object)

Object.ToString()

Namespace: NetTopologySuite.Operation.Linemerge

Assembly: NetTopologySuite.dll

Syntax

public class LineSequencer

Methods

Add(Geometry)

Adds a Geometry to be sequenced. May be called multiple times. Any dimension of Geometry may be added; the constituent linework will be extracted.

Declaration

public void Add(Geometry geometry)

Parameters

Type	Name	Description
Geometry	geometry

Add(IEnumerable<Geometry>)

Adds a IEnumerable<T> of Geometrys to be sequenced. May be called multiple times. Any dimension of Geometry may be added; the constituent linework will be extracted.

Declaration

public void Add(IEnumerable<Geometry> geometries)

Parameters

Type	Name	Description
IEnumerable<Geometry>	geometries	A IEnumerable<T> of geometries to add.

GetSequencedLineStrings()

Returns the LineString or MultiLineString built by the sequencing process, if one exists.

Declaration

public Geometry GetSequencedLineStrings()

Returns

Type	Description
Geometry	The sequenced linestrings, or null if a valid sequence does not exist.

IsSequenceable()

Tests whether the arrangement of linestrings has a valid sequence.

Declaration

public bool IsSequenceable()

Returns

Type	Description
Boolean	true if a valid sequence exists.

IsSequenced(Geometry)

Tests whether a Geometry is sequenced correctly. LineStrings are trivially sequenced. MultiLineStrings are checked for correct sequencing. Otherwise, IsSequenced is defined to be true for geometries that are not lineal.

Declaration

public static bool IsSequenced(Geometry geom)

Parameters

Type	Name	Description
Geometry	geom	The Geometry to test.

Returns

Type	Description
Boolean	true if the Geometry is sequenced or is not lineal.