org.opengis.geometry

Interface Geometry

All Superinterfaces:

TransfiniteSet

All Known Subinterfaces:

Aggregate, Boundary, Complex, ComplexBoundary, Composite, CompositeCurve, CompositePoint, CompositeSolid, CompositeSurface, Curve, CurveBoundary, MultiCurve, MultiPoint, MultiPrimitive, MultiSurface, OrientableCurve, OrientablePrimitive, OrientableSurface, Point, PolyhedralSurface, Primitive, PrimitiveBoundary, Ring, Shell, Solid, SolidBoundary, Surface, SurfaceBoundary, Tin, TriangulatedSurface

@UML(identifier="GM_Object",
     specification=ISO_19107)
public interface Geometry
extends TransfiniteSet

Root class of the geometric object taxonomy. Geometry supports interfaces common to all geographically referenced geometric objects. Geometry instances are sets of direct positions in a particular coordinate reference system. A Geometry can be regarded as an infinite set of points that satisfies the set operation interfaces for a set of direct positions, TransfiniteSet<DirectPosition>.

Since:

GeoAPI 1.0

Author:

Martin Desruisseaux (IRD)

Method Summary

Modifier and Type	Method and Description
Geometry	clone() Returns a clone of this geometry with deep copy semantic.
double	distance(Geometry geometry) Returns the distance between this Geometry and another Geometry.
Boundary	getBoundary() Returns a finite set of Geometrys containing all of the direct positions on the boundary of this Geometry.
Geometry	getBuffer(double distance) Returns a Geometry containing all points whose distance from this Geometry is less than or equal to the distance passed as a parameter.
DirectPosition	getCentroid() Returns the mathematical centroid for this Geometry.
Complex	getClosure() Returns a finite set of Geometrys containing all of the points on the boundary of this Geometry and this object (the union of the object and its boundary).
Geometry	getConvexHull() Returns a Geometry that represents the convex hull of this Geometry.
int	getCoordinateDimension() Returns the dimension of the coordinates that define this Geometry, which must be the same as the coordinate dimension of the coordinate reference system for this Geometry.
CoordinateReferenceSystem	getCoordinateReferenceSystem() Returns the coordinate reference system used in direct position coordinates.
int	getDimension(DirectPosition point) Returns the inherent dimension of this Geometry, which shall be less than or equal to the coordinate dimension.
Envelope	getEnvelope() Returns the minimum bounding box for this Geometry.
Set<? extends Complex>	getMaximalComplex() Returns the set of maximal complexes within which this Geometry is contained.
Geometry	getMbRegion() Returns a region in the coordinate reference system that contains this Geometry.
Precision	getPrecision() Returns the precision model used to guide the accuracy of topology operations.
DirectPosition	getRepresentativePoint() Returns a point value that is guaranteed to be on this Geometry.
boolean	isCycle() Returns true if this Geometry has an empty boundary after topological simplification (removal of overlaps between components in non-structured aggregates, such as subclasses of Aggregate).
boolean	isMutable() Returns false if this geometry is immutable.
boolean	isSimple() Returns true if this Geometry has no interior point of self-intersection or selftangency.
Geometry	toImmutable() Returns an immutable copy of this geometry.
Geometry	transform(CoordinateReferenceSystem newCRS) Returns a new Geometry that is the coordinate transformation of this Geometry into the passed coordinate reference system within the accuracy of the transformation.
Geometry	transform(CoordinateReferenceSystem newCRS, MathTransform transform) Returns a new Geometry that is the coordinate transformation of this Geometry into the passed coordinate reference system, using the specified transform.

Methods inherited from interface TransfiniteSet

contains, contains, difference, equals, intersection, intersects, symmetricDifference, union

Method Detail

getCoordinateReferenceSystem

@UML(identifier="CRS",
     obligation=MANDATORY,
     specification=ISO_19107)
CoordinateReferenceSystem getCoordinateReferenceSystem()

Returns the coordinate reference system used in direct position coordinates. If null, then this Geometry uses the coordinate reference system from another Geometry in which it is contained.

The most common example where the coordinate reference system is null is the elements and subcomplexes of a maximal complex. The complex can carry the coordinate reference system for all primitive elements and for all Complex subcomplexes.

This association is only navigable from Geometry to coordinate reference system. This means that the coordinate reference system objects in a data set do not keep a list of Geometrys that use them.

Returns:

The coordinate reference system used in direct position coordinates.

See Also:

getCoordinateDimension()

getPrecision

Precision getPrecision()

Returns the precision model used to guide the accuracy of topology operations.

Returns:

the precision model used for topological operations.

getMbRegion

@UML(identifier="mbRegion",
     obligation=MANDATORY,
     specification=ISO_19107)
Geometry getMbRegion()

Returns a region in the coordinate reference system that contains this Geometry. The default shall be to return an instance of an appropriate Geometry subclass that represents the same spatial set returned from getEnvelope(). The most common use of mbRegion will be to support indexing methods that use extents other than minimum bounding rectangles (MBR or envelopes). This does not restrict the returned Geometry from being a non-vector geometric representation, although those types are not defined within this specification.

Returns:

The minimum bounding region.

See Also:

getEnvelope(), getBoundary()

getRepresentativePoint

@UML(identifier="representativePoint",
     obligation=MANDATORY,
     specification=ISO_19107)
DirectPosition getRepresentativePoint()

Returns a point value that is guaranteed to be on this Geometry. The default logic may be to use the direct position of the point returned by getCentroid() if that point is on the object. Another use of representative point may be for the placement of labels in systems based on graphic presentation.

Returns:

The representative point.

See Also:

getCentroid()

getBoundary

@UML(identifier="boundary",
     obligation=MANDATORY,
     specification=ISO_19107)
Boundary getBoundary()

Returns a finite set of Geometrys containing all of the direct positions on the boundary of this Geometry. These object collections shall have further internal structure where appropriate. The finite set of Geometrys returned shall be in the same coordinate reference system as this Geometry. If the Geometry is in a complex, then the boundary Geometrys returned shall be in the same complex. If the Geometry is not in any complex, then the boundary Geometrys returned may have been constructed in response to the operation. The elements of a boundary shall be smaller in dimension than the original element.

Returns:

The sets of positions on the boundary.

See Also:

getMbRegion(), getClosure(), getBuffer(double), #getDistance

getClosure

@UML(identifier="closure",
     obligation=MANDATORY,
     specification=ISO_19107)
Complex getClosure()

Returns a finite set of Geometrys containing all of the points on the boundary of this Geometry and this object (the union of the object and its boundary). These object collections shall have further internal structure where appropriate. The finite set of Geometrys returned shall be in the same coordinate reference system as this Geometry. If the Geometry is in a complex, then the boundary Geometrys returned shall be in the same complex. If the Geometry is not in any complex, then the boundary Geometrys returned may have been constructed in response to the operation.

Returns:

The sets of points on the union of this object and its boundary.

See Also:

getBoundary()

isSimple

@UML(identifier="isSimple",
     obligation=MANDATORY,
     specification=ISO_19107)
boolean isSimple()

Returns true if this Geometry has no interior point of self-intersection or selftangency. In mathematical formalisms, this means that every point in the interior of the object must have a metric neighborhood whose intersection with the object is isomorphic to an n-sphere, where n is the dimension of this Geometry.

Since most coordinate geometries are represented, either directly or indirectly by functions from regions in Euclidean space of their topological dimension, the easiest test for simplicity to require that a function exist that is one-to-one and bicontinuous (continuous in both directions). Such a function is a topological isomorphism. This test does not work for "closed" objects (that is, objects for which isCycle() returns true).

Returns:

true if this object has no interior point of self-intersection or selftangency.

See Also:

isCycle()

isCycle

@UML(identifier="isCycle",
     obligation=MANDATORY,
     specification=ISO_19107)
boolean isCycle()

Returns true if this Geometry has an empty boundary after topological simplification (removal of overlaps between components in non-structured aggregates, such as subclasses of Aggregate). This condition is alternatively referred to as being "closed" as in a "closed curve." This creates some confusion since there are two distinct and incompatible definitions for the word "closed". The use of the word cycle is rarer (generally restricted to the field of algebraic topology), but leads to less confusion. Essentially, an object is a cycle if it is isomorphic to a geometric object that is the boundary of a region in some Euclidean space. Thus a curve is a cycle if it is isomorphic to a circle (has the same start and end point). A surface is a cycle if it isomorphic to the surface of a sphere, or some torus. A solid, with finite size, in a space of dimension 3 is never a cycle.

Returns:

true if this Geometry has an empty boundary after topological simplification.

See Also:

isSimple()

distance

@UML(identifier="distance",
     obligation=MANDATORY,
     specification=ISO_19107)
double distance(Geometry geometry)

Returns the distance between this Geometry and another Geometry. This distance is defined to be the greatest lower bound of the set of distances between all pairs of points that include one each from each of the two Geometrys. A "distance" value shall be a positive number associated to a distance unit such as meter or standard foot. If necessary, the second geometric object shall be transformed into the same coordinate reference system as the first before the distance is calculated.

If the geometric objects overlap, or touch, then their distance apart shall be zero. Some current implementations use a "negative" distance for such cases, but the approach is neither consistent between implementations, nor theoretically viable.

NOTE: The role of the reference system in distance calculations is important. Generally, there are at least three types of distances that may be defined between points (and therefore between geometric objects): map distance, geodesic distance, and terrain distance.

• Map distance is the distance between the points as defined by their positions in a coordinate projection (such as on a map when scale is taken into account). Map distance is usually accurate for small areas where scale functions have well-behaved derivatives.
• Geodesic distance is the length of the shortest curve between those two points along the surface of the earth model being used by the coordinate reference system. Geodesic distance behaves well for wide areas of coverage, and takes the earth's curvature into account. It is especially handy for air and sea navigation, although care should be taken to distinguish between rhumb line (curves of constant bearing) and geodesic curve distance.
• Terrain distance takes into account the local vertical displacements (hypsography). Terrain distance can be based either on a geodesic distance or a map distance.

Parameters:

geometry - The other object.

Returns:

The distance between the two objects.

Since:

GeoAPI 2.1

See Also:

getBoundary(), getBuffer(double), CoordinateSystem.getAxis(int)

getDimension

@UML(identifier="dimension",
     obligation=MANDATORY,
     specification=ISO_19107)
int getDimension(DirectPosition point)

Returns the inherent dimension of this Geometry, which shall be less than or equal to the coordinate dimension. The dimension of a collection of geometric objects shall be the largest dimension of any of its pieces. Points are 0-dimensional, curves are 1-dimensional, surfaces are 2-dimensional, and solids are 3-dimensional. Locally, the dimension of a geometric object at a point is the dimension of a local neighborhood of the point - that is the dimension of any coordinate neighborhood of the point. Dimension is unambiguously defined only for direct positions interior to this Geometry. If the passed direct position is null, then the operation shall return the largest possible dimension for any direct position in this Geometry.

Parameters:

point - The point where to evaluate the dimension, or null.

Returns:

The inherent dimension.

See Also:

getCoordinateDimension()

getCoordinateDimension

@UML(identifier="coordinateDimension",
     obligation=MANDATORY,
     specification=ISO_19107)
int getCoordinateDimension()

Returns the dimension of the coordinates that define this Geometry, which must be the same as the coordinate dimension of the coordinate reference system for this Geometry.

Returns:

The coordinate dimension.

See Also:

getDimension(org.opengis.geometry.DirectPosition), getCoordinateReferenceSystem()

getMaximalComplex

@UML(identifier="maximalComplex",
     obligation=MANDATORY,
     specification=ISO_19107)
Set<? extends Complex> getMaximalComplex()

Returns the set of maximal complexes within which this Geometry is contained. As a set of primitives, a complex may be contained as a set in another larger complex, referred to as a "super complex" of the original. A complex is maximal if there is no such larger super complex.

Returns:

The set of maximal complexes within which this Geometry is contained.

transform

@UML(identifier="transform",
     obligation=MANDATORY,
     specification=ISO_19107)
Geometry transform(CoordinateReferenceSystem newCRS)
                                                                                                  throws TransformException

Returns a new Geometry that is the coordinate transformation of this Geometry into the passed coordinate reference system within the accuracy of the transformation.

Parameters:

newCRS - The new coordinate reference system.

Returns:

The transformed Geometry.

Throws:

TransformException - if the transformation failed.

transform

@Extension
Geometry transform(CoordinateReferenceSystem newCRS,
                              MathTransform transform)
                       throws TransformException

Returns a new Geometry that is the coordinate transformation of this Geometry into the passed coordinate reference system, using the specified transform. It is the user responsability to ensure that the supplied transform is appropriate for this geometry.

Parameters:

newCRS - The new coordinate reference system.

transform - The transform from the existing coordinate reference system to the new coordinate reference system.

Returns:

The transformed Geometry.

Throws:

TransformException - if the transformation failed.

getEnvelope

@UML(identifier="envelope",
     obligation=MANDATORY,
     specification=ISO_19107)
Envelope getEnvelope()

Returns the minimum bounding box for this Geometry. This shall be the coordinate region spanning the minimum and maximum value for each ordinate taken on by direct positions in this Geometry. The simplest representation for an envelope consists of two direct positions, the first one containing all the minimums for each ordinate, and second one containing all the maximums. However, there are cases for which these two positions would be outside the domain of validity of the object's coordinate reference system.

Returns:

The envelope.

See Also:

getMbRegion()

getCentroid

@UML(identifier="centroid",
     obligation=MANDATORY,
     specification=ISO_19107)
DirectPosition getCentroid()

Returns the mathematical centroid for this Geometry. The result is not guaranteed to be on the object. For heterogeneous collections of primitives, the centroid only takes into account those of the largest dimension. For example, when calculating the centroid of surfaces, an average is taken weighted by area. Since curves have no area they do not contribute to the average.

Returns:

The centroid.

See Also:

getRepresentativePoint()

getConvexHull

@UML(identifier="convexHull",
     obligation=MANDATORY,
     specification=ISO_19107)
Geometry getConvexHull()

Returns a Geometry that represents the convex hull of this Geometry. Convexity requires the use of "lines" or "curves of shortest length" and the use of different coordinate systems may result in different versions of the convex hull of an object. Each implementation shall decide on an appropriate solution to this ambiguity. For two reasonable coordinate systems, a convex hull of an object in one will be very closely approximated by the transformed image of the convex hull of the same object in the other.

Returns:

The convex hull.

getBuffer

@UML(identifier="buffer",
     obligation=MANDATORY,
     specification=ISO_19107)
Geometry getBuffer(double distance)

Returns a Geometry containing all points whose distance from this Geometry is less than or equal to the distance passed as a parameter. The Geometry returned is in the same reference system as this original Geometry. The dimension of the returned Geometry is normally the same as the coordinate dimension - a collection of surfaces in 2D space and a collection of solids in 3D space, but this may be application defined.

Parameters:

distance - The distance.

Returns:

A geometry containing all points whose distance from this Geometry is less than or equal to the specified distance.

See Also:

getBoundary(), #getDistance, CoordinateSystem.getAxis(int)

isMutable

@Extension
boolean isMutable()

Returns false if this geometry is immutable. Immutable geometries are guarantee to never change their state, neither directly (through a change in this object) or indirectly (through a change in an other object this geometry depends upon). Immutable geometries avoid the need for cloning them. More specifically:

• If false, then this geometry is immutable. It is guarantee that a call to any setFoo(...) method will throws an UnmodifiableGeometryException (that said, immutable geometries are necessarily unmodifiable. The converse is not true, see next point below). This geometry will never change its state, and there is no need for cloning it.

• If true, then this geometry is mutable. Note that mutable geometry is not synonymous of modifiable geometry. The nuance lays in whatever the geometry may changes its state directly (as of user request) or indirectly:

  • This geometry may be modifiable, in which case invoking setFoo(...) methods is legal and will not throws exception.

  • This geometry may still unmodifiable. User is not allowed to modify it himself and invoking any setFoo(...) method will throws an UnmodifiableGeometryException. However, the implementation may change the geometry itself (for example a time-varying geometry).

Returns:

true if this geometry is mutable.

toImmutable

@Extension
Geometry toImmutable()

Returns an immutable copy of this geometry. The returned Geometry is guaranteed to have an isMutable() value of false. Moreover, as per the contract of isMutable(), its values will never change. Any attempts to change the values of the returned object will result in a UnmodifiableGeometryException.

Implementors are free to return this if this object is already immutable.

Returns:

An immutable copy of this geometry.

clone

Geometry clone()
        throws CloneNotSupportedException

Returns a clone of this geometry with deep copy semantic. Any change on this object will have no impact on the returned clone, and conversely. For big geometries, implementations are encouraged to share as much internal data as possible (as opposed to performing a real copy of the data), while preserving the deep copy semantic.

Special cases:

• If this geometry is immutable (isMutable() == false), then there is no need for cloning this object. This method may return this or returns a modifiable copy of this object, at implementation choice.

• If a deep copy semantic is not possible at a reasonable cost (for example for some database backend), then this method throws a CloneNotSupportedException.

• If a deep cloning is possible for all case (i.e. if this method never throws CloneNotSupportedException), then the implementation should implements the Cloneable interface.

Returns:

A clone of this geometry, which may or may not be mutable.

Throws:

CloneNotSupportedException - if this object do not support clone. This exception is never throws if this object implements Cloneable.

See Also:

Cloneable, isMutable()