geos::operation::distance::IndexedFacetDistance Class Reference

Computes the distance between the facets (segments and vertices) of two Geometrys using a Branch-and-Bound algorithm. More...

#include <IndexedFacetDistance.h>

Public Member Functions
	IndexedFacetDistance (const geom::Geometry *g)
	Creates a new distance-finding instance for a given target geom::Geometry. More...
double	distance (const geom::Geometry *g) const
	Computes the distance from the base geometry to the given geometry. More...
std::vector< GeometryLocation >	nearestLocations (const geom::Geometry *g) const
	Computes the nearest locations on the base geometry and the given geometry. More...
std::vector< geom::Coordinate >	nearestPoints (const geom::Geometry *g) const
	Compute the nearest locations on the target geometry and the given geometry. More...

Static Public Member Functions
static double	distance (const geom::Geometry *g1, const geom::Geometry *g2)
	Computes the distance between facets of two geometries. More...
static std::vector< geom::Coordinate >	nearestPoints (const geom::Geometry *g1, const geom::Geometry *g2)
	Computes the nearest points of the facets of two geometries. More...

Private Attributes
std::unique_ptr< geos::index::strtree::STRtree >	cachedTree

Detailed Description

Computes the distance between the facets (segments and vertices) of two Geometrys using a Branch-and-Bound algorithm.

The Branch-and-Bound algorithm operates over a traversal of R-trees built on the target and the query geometries.

This approach provides the following benefits:

• Performance is dramatically improved due to the use of the R-tree index and the pruning due to the Branch-and-Bound approach
• The spatial index on the target geometry is cached which allow reuse in an repeated query situation.

Using this technique is usually much more performant than using the brute-force geom::Geometry::distance(const Geometry* g) const when one or both input geometries are large, or when evaluating many distance computations against a single geometry.

Author

Martin Davis

Definition at line 47 of file IndexedFacetDistance.h.

Constructor & Destructor Documentation

geos::operation::distance::IndexedFacetDistance::IndexedFacetDistance ( const geom::Geometry *  g )

inline

Creates a new distance-finding instance for a given target geom::Geometry.

Distances will be computed to all facets of the input geometry. The facets of the geometry are the discrete segments and points contained in its components. In the case of lineal and puntal inputs, this is equivalent to computing the conventional distance. In the case of polygonal inputs, this is equivalent to computing the distance to the polygon boundaries.

Parameters

g	a Geometry, which may be of any type.

Definition at line 61 of file IndexedFacetDistance.h.

Member Function Documentation

static double geos::operation::distance::IndexedFacetDistance::distance ( const geom::Geometry *  g1, const geom::Geometry *  g2  )

static

Computes the distance between facets of two geometries.

For geometries with many segments or points, this can be faster than using a simple distance algorithm.

Parameters

g1	a geometry
g2	a geometry

Returns

the distance between facets of the geometries

double geos::operation::distance::IndexedFacetDistance::distance

(

const geom::Geometry *

g

)

const

Computes the distance from the base geometry to the given geometry.

Parameters

g	the geometry to compute the distance to

Returns

the computed distance

std::vector<GeometryLocation> geos::operation::distance::IndexedFacetDistance::nearestLocations

(

const geom::Geometry *

g

)

const

Computes the nearest locations on the base geometry and the given geometry.

Parameters

g	the geometry to compute the nearest location to

Returns

the nearest locations

static std::vector<geom::Coordinate> geos::operation::distance::IndexedFacetDistance::nearestPoints ( const geom::Geometry *  g1, const geom::Geometry *  g2  )

static

Computes the nearest points of the facets of two geometries.

Parameters

g1	a geometry
g2	a geometry

Returns

the nearest points on the facets of the geometries

std::vector<geom::Coordinate> geos::operation::distance::IndexedFacetDistance::nearestPoints

(

const geom::Geometry *

g

)

const

Compute the nearest locations on the target geometry and the given geometry.

Parameters

g	the geometry to compute the nearest point to

Returns

the nearest points

Member Data Documentation

std::unique_ptr<geos::index::strtree::STRtree> geos::operation::distance::IndexedFacetDistance::cachedTree

private

Definition at line 102 of file IndexedFacetDistance.h.

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

• IndexedFacetDistance.h