org.locationtech.jts.operation.overlay.snap

Class GeometrySnapper

java.lang.Object

org.locationtech.jts.operation.overlay.snap.GeometrySnapper

public class GeometrySnapper
extends Object

Snaps the vertices and segments of a Geometry to another Geometry's vertices. A snap distance tolerance is used to control where snapping is performed. Snapping one geometry to another can improve robustness for overlay operations by eliminating nearly-coincident edges (which cause problems during noding and intersection calculation). It can also be used to eliminate artifacts such as narrow slivers, spikes and gores.

Too much snapping can result in invalid topology being created, so the number and location of snapped vertices is decided using heuristics to determine when it is safe to snap. This can result in some potential snaps being omitted, however.

Version:

1.7

Author:

Martin Davis

Constructor Summary

Constructors

Constructor and Description
GeometrySnapper(Geometry srcGeom) Creates a new snapper acting on the given geometry

Method Summary

Modifier and Type	Method and Description
static double	computeOverlaySnapTolerance(Geometry g) Estimates the snap tolerance for a Geometry, taking into account its precision model.
static double	computeOverlaySnapTolerance(Geometry g0, Geometry g1)
static double	computeSizeBasedSnapTolerance(Geometry g)
static Geometry[]	snap(Geometry g0, Geometry g1, double snapTolerance) Snaps two geometries together with a given tolerance.
Geometry	snapTo(Geometry snapGeom, double snapTolerance) Snaps the vertices in the component LineStrings of the source geometry to the vertices of the given snap geometry.
Geometry	snapToSelf(double snapTolerance, boolean cleanResult) Snaps the vertices in the component LineStrings of the source geometry to the vertices of the same geometry.
static Geometry	snapToSelf(Geometry geom, double snapTolerance, boolean cleanResult) Snaps a geometry to itself.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

GeometrySnapper

public GeometrySnapper(Geometry srcGeom)

Creates a new snapper acting on the given geometry

Parameters:

srcGeom - the geometry to snap

Method Detail

computeOverlaySnapTolerance

public static double computeOverlaySnapTolerance(Geometry g)

Estimates the snap tolerance for a Geometry, taking into account its precision model.

Parameters:

g - a Geometry

Returns:

the estimated snap tolerance

computeSizeBasedSnapTolerance

public static double computeSizeBasedSnapTolerance(Geometry g)

computeOverlaySnapTolerance

public static double computeOverlaySnapTolerance(Geometry g0,
                                                 Geometry g1)

snap

public static Geometry[] snap(Geometry g0,
                              Geometry g1,
                              double snapTolerance)

Snaps two geometries together with a given tolerance.

Parameters:

g0 - a geometry to snap

g1 - a geometry to snap

snapTolerance - the tolerance to use

Returns:

the snapped geometries

snapToSelf

public static Geometry snapToSelf(Geometry geom,
                                  double snapTolerance,
                                  boolean cleanResult)

Snaps a geometry to itself. Allows optionally cleaning the result to ensure it is topologically valid (which fixes issues such as topology collapses in polygonal inputs).

Snapping a geometry to itself can remove artifacts such as very narrow slivers, gores and spikes.

Parameters:

geom - the geometry to snap

snapTolerance - the snapping tolerance

cleanResult - whether the result should be made valid

Returns:

a new snapped Geometry

snapTo

public Geometry snapTo(Geometry snapGeom,
                       double snapTolerance)

Snaps the vertices in the component LineStrings of the source geometry to the vertices of the given snap geometry.

Parameters:

snapGeom - a geometry to snap the source to

Returns:

a new snapped Geometry

snapToSelf

public Geometry snapToSelf(double snapTolerance,
                           boolean cleanResult)

Snaps the vertices in the component LineStrings of the source geometry to the vertices of the same geometry. Allows optionally cleaning the result to ensure it is topologically valid (which fixes issues such as topology collapses in polygonal inputs).

Parameters:

snapTolerance - the snapping tolerance

cleanResult - whether the result should be made valid

Returns:

a new snapped Geometry