GEOS
3.3.4
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Builds a sequence from a set of LineStrings so that they are ordered end to end. More...
#include <LineSequencer.h>
Public Member Functions | |
bool | isSequenceable () |
void | add (const geom::Geometry &geometry) |
template<class TargetContainer > | |
void | add (TargetContainer &geoms) |
void | filter (const geom::Geometry *g) |
geom::Geometry * | getSequencedLineStrings (bool release=1) |
Static Public Member Functions | |
static geom::Geometry * | sequence (const geom::Geometry &geom) |
static bool | isSequenced (const geom::Geometry *geom) |
Builds a sequence from a set of LineStrings so that they are ordered end to end.
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.
A typical use case is to convert a set of unoriented geometric links from a linear network (e.g. such as block faces on a bus route) into a continuous oriented path through the network.
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 computed output 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:
Note that 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 method will return false
.
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inline |
Adds a Geometry to be sequenced. May be called multiple times. Any dimension of Geometry may be added; the constituent linework will be extracted.
geometry | the geometry to add |
References geos::geom::Geometry::applyComponentFilter().
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inline |
Act as a GeometryComponentFilter so to extract the linearworks
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Returns the LineString or MultiLineString built by the sequencing process, if one exists.
release | release ownership of computed Geometry |
null
if a valid sequence does not exist.
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inline |
Tests whether the arrangement of linestrings has a valid sequence.
true
if a valid sequence exists.
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static |
Tests whether a Geometry is sequenced correctly. { LineString}s are trivially sequenced. MultiLineStrings are checked for correct sequencing. Otherwise, isSequenced
is defined to be true
for geometries that are not lineal.
geom | the geometry to test |