geos::operation::overlayng::CoverageUnion Class Reference

#include <CoverageUnion.h>

Static Public Member Functions
static std::unique_ptr< Geometry >	geomunion (const Geometry *coverage)

Detailed Description

Unions a valid coverage of polygons or lines in an efficient way.

A valid polygonal coverage is a collection of geom::Polygon which satisfy the following conditions:

• Vector-clean - Line segments within the collection must either be identical or intersect only at endpoints.
• Non-overlapping - No two polygons may overlap. Equivalently, polygons must be interior-disjoint.

A valid linear coverage is a collection of geom::LineString which satisfies the Vector-clean condition. Note that this does not require the LineStrings to be fully noded

• i.e. they may contain coincident linework. Coincident line segments are dissolved by the union. Currently linear output is not merged (this may be added in a future release.)

Currently no checking is done to determine whether the input is a valid coverage. This is because coverage validation involves segment intersection detection, which is much more expensive than the union phase. If the input is not a valid coverage then in some cases this will be detected during processing and a util::TopologyException is thrown. Otherwise, the computation will produce output, but it will be invalid.

Unioning a valid coverage implies that no new vertices are created. This means that a precision model does not need to be specified. The precision of the vertices in the output geometry is not changed.

Author

Martin Davis

See also

noding::SegmentExtractingNoder

Member Function Documentation

geomunion()

static std::unique_ptr< Geometry > geos::operation::overlayng::CoverageUnion::geomunion ( const Geometry *  coverage )

static

Unions a valid polygonal coverage or linear network.

Parameters

coverage

a coverage of polygons or lines

Returns

the union of the coverage

Exceptions

util::TopologyException

in some cases if the coverage is invalid

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The documentation for this class was generated from the following file:

• overlayng/CoverageUnion.h