Table of Contents

Class Geometry

Namespace
NetTopologySuite.Geometries
Assembly
NetTopologySuite.dll

A representation of a planar, linear vector geometry.

public abstract class Geometry : IComparable, IComparable<Geometry>
Inheritance
Geometry
Implements
Derived
Inherited Members

Remarks

Binary Predicates:

Because it is not clear at this time what semantics for spatial analysis methods involving GeometryCollections would be useful, GeometryCollections are not supported as arguments to binary predicates or the Relate method.

Overlay Methods:

The spatial analysis methods will return the most specific class possible to represent the result. If the result is homogeneous, a Point, LineString, or Polygon will be returned if the result contains a single element; otherwise, a MultiPoint, MultiLineString, or MultiPolygon will be returned. If the result is heterogeneous a GeometryCollection will be returned.

Representation of Computed Geometries: The SFS states that the result of a set-theoretic method is the "point-set" result of the usual set-theoretic definition of the operation (SFS 3.2.21.1). However, there are sometimes many ways of representing a point set as a Geometry. The SFS does not specify an unambiguous representation of a given point set returned from a spatial analysis method. One goal of NTS is to make this specification precise and unambiguous. NTS uses a canonical form for Geometrys returned from overlay methods. The canonical form is a Geometry which is simple and noded: Simple means that the Geometry returned will be simple according to the NTS definition of IsSimple. Noded applies only to overlays involving LineStrings. It means that all intersection points on LineStrings will be present as endpoints of LineStrings in the result. This definition implies that non-simple geometries which are arguments to spatial analysis methods must be subjected to a line-dissolve process to ensure that the results are simple.

Constructed Points And The Precision Model: The results computed by the set-theoretic methods may contain constructed points which are not present in the input Geometrys. These new points arise from intersections between line segments in the edges of the input Geometrys. In the general case it is not possible to represent constructed points exactly. This is due to the fact that the coordinates of an intersection point may contain twice as many bits of precision as the coordinates of the input line segments. In order to represent these constructed points explicitly, NTS must truncate them to fit the PrecisionModel. Unfortunately, truncating coordinates moves them slightly. Line segments which would not be coincident in the exact result may become coincident in the truncated representation. This in turn leads to "topology collapses" -- situations where a computed element has a lower dimension than it would in the exact result. When NTS detects topology collapses during the computation of spatial analysis methods, it will throw an exception. If possible the exception will report the location of the collapse.

Geometry Equality

There are two ways of comparing geometries for equality: structural equality and topological equality.

Structural Equality

Structural Equality is provided by the EqualsExact(Geometry) method. This implements a comparison based on exact, structural pointwise equality. The Equals(object) is a synonym for this method, to provide structural equality semantics for use in collections. It is important to note that structural pointwise equality is easily affected by things like ring order and component order. In many situations it will be desirable to normalize geometries before comparing them (using the Normalized() or Normalize() methods). EqualsNormalized(Geometry) is provided as a convenience method to compute equality over normalized geometries, but it is expensive to use. Finally, EqualsExact(Geometry, double) allows using a tolerance value for point comparison.

Topological Equality

Topological Equality is provided by the EqualsTopologically(Geometry) method. It implements the SFS definition of point-set equality defined in terms of the DE-9IM matrix. To support the SFS naming convention, the method Equals(Geometry) is also provided as a synonym. However, due to the potential for confusion with Equals(object) its use is discouraged.

Since Equals(object) and GetHashCode() are overridden, Geometries can be used effectively in .Net collections.

Constructors

Geometry(GeometryFactory)

Creates a new Geometry via the specified GeometryFactory.

protected Geometry(GeometryFactory factory)

Parameters

factory GeometryFactory

The factory

Fields

DefaultFactory

A predefined GeometryFactory with PrecisionModel == Fixed.

public static readonly GeometryFactory DefaultFactory

Field Value

GeometryFactory
See Also

TypeNameGeometryCollection

The name of geometry collection geometries.

public const string TypeNameGeometryCollection = "GeometryCollection"

Field Value

string

TypeNameLineString

The name of linestring geometries

public const string TypeNameLineString = "LineString"

Field Value

string

TypeNameLinearRing

The name of linearring geometries

public const string TypeNameLinearRing = "LinearRing"

Field Value

string

TypeNameMultiLineString

The name of multi-linestring geometries

public const string TypeNameMultiLineString = "MultiLineString"

Field Value

string

TypeNameMultiPoint

The name of multi-point geometries

public const string TypeNameMultiPoint = "MultiPoint"

Field Value

string

TypeNameMultiPolygon

The name of multi-polygon geometries

public const string TypeNameMultiPolygon = "MultiPolygon"

Field Value

string

TypeNamePoint

The name of point geometries

public const string TypeNamePoint = "Point"

Field Value

string

TypeNamePolygon

The name of polygon geometries

public const string TypeNamePolygon = "Polygon"

Field Value

string

Properties

Area

Returns the area of this Geometry. Areal Geometries have a non-zero area. They override this function to compute the area. Others return 0.0

public virtual double Area { get; }

Property Value

double

The area of the Geometry.

Boundary

Returns the boundary, or an empty geometry of appropriate dimension if this Geometry is empty. For a discussion of this function, see the OpenGIS Simple Features Specification. As stated in SFS Section 2.1.13.1, "the boundary of a Geometry is a set of Geometries of the next lower dimension."

public abstract Geometry Boundary { get; }

Property Value

Geometry

The closure of the combinatorial boundary of this Geometry.

BoundaryDimension

Returns the dimension of this Geometrys inherent boundary.

public abstract Dimension BoundaryDimension { get; }

Property Value

Dimension

The dimension of the boundary of the class implementing this interface, whether or not this object is the empty point. Returns Dimension.False if the boundary is the empty point.

Centroid

Computes the centroid of this Geometry. The centroid is equal to the centroid of the set of component Geometries of highest dimension (since the lower-dimension geometries contribute zero "weight" to the centroid).

The centroid of an empty geometry is POINT EMPTY. 
public virtual Point Centroid { get; }

Property Value

Point

A Point which is the centroid of this Geometry.

Coordinate

Returns a vertex of this Geometry (usually, but not necessarily, the first one).

public abstract Coordinate Coordinate { get; }

Property Value

Coordinate

a Coordinate which is a vertex of this Geometry.

Remarks

The returned coordinate should not be assumed to be an actual Coordinate object used in the internal representation.

Coordinates

Returns an array containing the values of all the vertices for this geometry.

public abstract Coordinate[] Coordinates { get; }

Property Value

Coordinate[]

The vertices of this Geometry.

Remarks

If the geometry is a composite, the array will contain all the vertices for the components, in the order in which the components occur in the geometry.

In general, the array cannot be assumed to be the actual internal storage for the vertices. Thus modifying the array may not modify the geometry itself. Use the SetOrdinate(int, int, double) or SetOrdinate(int, Ordinate, double) method (possibly on the components) to modify the underlying data. If the coordinates are modified, GeometryChanged() must be called afterwards.

See Also

Dimension

Returns the dimension of this geometry.

public abstract Dimension Dimension { get; }

Property Value

Dimension

The topological dimensions of this geometry

Remarks

The dimension of a geometry is is the topological dimension of its embedding in the 2-D Euclidean plane. In the NTS spatial model, dimension values are in the set {0,1,2}.

Note that this is a different concept to the dimension of the vertex Coordinates. The geometry dimension can never be greater than the coordinate dimension. For example, a 0-dimensional geometry (e.g. a Point) may have a coordinate dimension of 3 (X,Y,Z).

Envelope

Gets a geometry representing the envelope (bounding box) of this Geometry.

public Geometry Envelope { get; }

Property Value

Geometry

A Geometry representing the envelope of this Geometry

Remarks

If this Geometry is

  • empty, returns an empty Point
  • a point, returns a Point
  • a line parallel to an axis, a two-vertex LineString,
  • otherwise, returns a Polygon whose vertices are (minx, miny), (maxx, miny), (maxx, maxy), (minx, maxy), (minx, miny).
See Also

EnvelopeInternal

Gets an Envelope containing the minimum and maximum x and y values in this Geometry. If the geometry is empty, an empty Envelope is returned.

public Envelope EnvelopeInternal { get; }

Property Value

Envelope

the envelope of this Geometry.

Remarks

The returned object is a copy of the one maintained internally, to avoid aliasing issues. For best performance, clients which access this envelope frequently should cache the return value.

Factory

Gets the factory which contains the context in which this point was created.

public GeometryFactory Factory { get; }

Property Value

GeometryFactory

The factory for this point.

GeometryType

Returns the name of this Geometry's actual class.

public abstract string GeometryType { get; }

Property Value

string

The name of this Geometrys actual class.

InteriorPoint

Computes an interior point of this Geometry.

public virtual Point InteriorPoint { get; }

Property Value

Point

A Point which is in the interior of this Geometry.

Remarks

An interior point is guaranteed to lie in the interior of the Geometry, if it possible to calculate such a point exactly. Otherwise, the point may lie on the boundary of the point.

The interior point of an empty geometry is POINT EMPTY.

IsEmpty

Tests whether the set of points covered in this Geometry is empty.

Note this test is for topological emptiness, not structural emptiness.
A collection containing only empty elements is reported as empty.
To check structural emptiness use NumGeometries. 
public abstract bool IsEmpty { get; }

Property Value

bool

true if this Geometry does not cover any points.

IsGeometryCollection

Tests whether this is an instance of a general {@link GeometryCollection}, rather than a homogeneous subclass.

protected bool IsGeometryCollection { get; }

Property Value

bool

true if this is a heterogeneous GeometryCollection

IsRectangle

Tests whether this is a rectangular Polygon.

public virtual bool IsRectangle { get; }

Property Value

bool

true if the geometry is a rectangle.

Remarks

Polygon overrides to check for actual rectangle.

IsSimple

Tests whether this Geometry is simple.

The SFS definition of simplicity follows the general rule that a Geometry is simple if it has no points of self-tangency, self-intersection or other anomalous points.

Simplicity is defined for each Geometry subclass as follows:
  • Valid polygonal geometries are simple, since their rings must not self-intersect. IsSimple tests for this condition and reports false if it is not met. (This is a looser test than checking for validity).
  • Linear rings have the same semantics.
  • Linear geometries are simple if they do not self-intersect at points other than boundary points.
  • Zero-dimensional geometries (points) are simple if they have no repeated points.
  • Empty Geometrys are always simple.
public virtual bool IsSimple { get; }

Property Value

bool

true if this Geometry is simple

See Also

IsValid

Tests whether this Geometry is topologically valid, according to the OGC SFS specification.

For validity rules see the documentation for the specific geometry subclass. 
public virtual bool IsValid { get; }

Property Value

bool

true if this Geometry is valid.

Length

Returns the length of this Geometry. Linear geometries return their length. Areal geometries return their perimeter. They override this function to compute the length. Others return 0.0

public virtual double Length { get; }

Property Value

double

The length of the Geometry.

NumGeometries

Returns the number of Geometryes in a GeometryCollection, or 1, if the geometry is not a collection.

public virtual int NumGeometries { get; }

Property Value

int

NumPoints

Returns the count of this Geometrys vertices. The Geometry s contained by composite Geometrys must be Geometry's; that is, they must implement NumPoints.

public abstract int NumPoints { get; }

Property Value

int

The number of vertices in this Geometry.

OgcGeometryType

Gets the OGC geometry type

public abstract OgcGeometryType OgcGeometryType { get; }

Property Value

OgcGeometryType

PointOnSurface

InteriorPoint

public Point PointOnSurface { get; }

Property Value

Point

PrecisionModel

Returns the PrecisionModel used by the Geometry.

public PrecisionModel PrecisionModel { get; }

Property Value

PrecisionModel

the specification of the grid of allowable points, for this Geometry and all other Geometrys.

SRID

Sets the ID of the Spatial Reference System used by the Geometry.

public int SRID { get; set; }

Property Value

int

Remarks

NOTE: This method should only be used for exceptional circumstances or for backwards compatibility. Normally the SRID should be set on the GeometryFactory used to create the geometry. SRIDs set using this method will change the Factory.

See Also

SortIndex

Gets a value to sort the geometry

protected abstract Geometry.SortIndexValue SortIndex { get; }

Property Value

Geometry.SortIndexValue

Remarks

NOTE:
For JTS v1.17 this property's getter has been renamed to getTypeCode(). In order not to break binary compatibility we did not follow.

UserData

Gets/Sets the user data object for this point, if any.

public object UserData { get; set; }

Property Value

object

Remarks

A simple scheme for applications to add their own custom data to a Geometry. An example use might be to add an object representing a Coordinate Reference System. Note that user data objects are not present in geometries created by construction methods.

Methods

Apply(ICoordinateFilter)

Performs an operation with or on this Geometry's coordinates.

public abstract void Apply(ICoordinateFilter filter)

Parameters

filter ICoordinateFilter

The filter to apply to this Geometry's coordinates

Remarks

If this method modifies any coordinate values, GeometryChanged() must be called to update the geometry state. Note that you cannot use this method to modify this Geometry if its underlying CoordinateSequence's #get method returns a copy of the Coordinate, rather than the actual Coordinate stored (if it even stores Coordinate objects at all).

Apply(ICoordinateSequenceFilter)

Performs an operation on the coordinates in this Geometry's CoordinateSequences.

public abstract void Apply(ICoordinateSequenceFilter filter)

Parameters

filter ICoordinateSequenceFilter

The filter to apply

Remarks

If the filter reports that a coordinate value has been changed, GeometryChanged() will be called automatically.

Apply(IEntireCoordinateSequenceFilter)

Performs an operation on this Geometry's CoordinateSequences.

public virtual void Apply(IEntireCoordinateSequenceFilter filter)

Parameters

filter IEntireCoordinateSequenceFilter

The filter to apply

Remarks

If the filter reports that a coordinate value has been changed, GeometryChanged() will be called automatically.

Apply(IGeometryComponentFilter)

Performs an operation with or on this Geometry and its component Geometry's. Only GeometryCollections and Polygons have component Geometry's; for Polygons they are the LinearRings of the shell and holes.

public abstract void Apply(IGeometryComponentFilter filter)

Parameters

filter IGeometryComponentFilter

The filter to apply to this Geometry.

Apply(IGeometryFilter)

Performs an operation with or on this Geometry and its subelement Geometrys (if any). Only GeometryCollections and subclasses have subelement Geometry's.

public abstract void Apply(IGeometryFilter filter)

Parameters

filter IGeometryFilter

The filter to apply to this Geometry (and its children, if it is a GeometryCollection).

AsBinary()

ToBinary()

public byte[] AsBinary()

Returns

byte[]

AsText()

ToText()

public string AsText()

Returns

string

Buffer(double)

Computes a buffer area around this geometry having the given width. The buffer of a Geometry is the Minkowski sum or difference of the geometry with a disc of radius Abs(distance).

public Geometry Buffer(double distance)

Parameters

distance double

The width of the buffer (may be positive, negative or 0), interpreted according to the PrecisionModel of the Geometry.

Returns

Geometry

a polygonal geometry representing the buffer region (which may be empty)

Remarks

Mathematically-exact buffer area boundaries can contain circular arcs. To represent these arcs using linear geometry they must be approximated with line segments. The buffer geometry is constructed using 8 segments per quadrant to approximate the circular arcs.

The end cap style is EndCapStyle.Round.

The buffer operation always returns a polygonal result. The negative or zero-distance buffer of lines and points is always an empty IPolygonal. This is also the result for the buffers of degenerate (zero-area) polygons.

Exceptions

TopologyException

If a robustness error occurs

See Also

Buffer(double, BufferParameters)

Computes a buffer region around this Geometry having the given width and with a specified number of segments used to approximate curves. The buffer of a Geometry is the Minkowski sum of the Geometry with a disc of radius distance. Curves in the buffer polygon are approximated with line segments. This method allows specifying the accuracy of that approximation.

public Geometry Buffer(double distance, BufferParameters bufferParameters)

Parameters

distance double

The width of the buffer, interpreted according to the PrecisionModel of the Geometry.

bufferParameters BufferParameters

This argument type has a number of properties that control the construction of the buffer, including QuadrantSegments, EndCapStyle, JoinStyle, and MitreLimit

Returns

Geometry

a polygonal geometry representing the buffer region (which may be empty)

Remarks

Mathematically-exact buffer area boundaries can contain circular arcs. To represent these arcs using linear geometry they must be approximated with line segments. The bufferParameters argument has a property QuadrantSegments controlling the accuracy of the approximation by specifying the number of line segments used to represent a quadrant of a circle

The EndCapStyle property of the bufferParameters argument specifies the buffer geometry that will be created at the ends of linestrings. The styles provided are:

  • Round - (default) a semi-circle
  • Flat - a straight line perpendicular to the end segment
  • Square - a half-square

The buffer operation always returns a polygonal result. The negative or zero-distance buffer of lines and points is always an empty IPolygonal. This is also the result for the buffers of degenerate (zero-area) polygons.

Exceptions

TopologyException

If a robustness error occurs

See Also

Buffer(double, EndCapStyle)

Computes a buffer region around this Geometry having the given width. The buffer of a Geometry is the Minkowski sum or difference of the geometry with a disc of radius Abs(distance).

public Geometry Buffer(double distance, EndCapStyle endCapStyle)

Parameters

distance double

The width of the buffer, interpreted according to the PrecisionModel of the Geometry.

endCapStyle EndCapStyle

Cap Style to use for compute buffer.

Returns

Geometry

a polygonal geometry representing the buffer region (which may be empty)

Remarks

The end cap style specifies the buffer geometry that will be created at the ends of linestrings. The styles provided are:

  • Round - (default) a semi-circle
  • Flat - a straight line perpendicular to the end segment
  • Square - a half-square

The buffer operation always returns a polygonal result. The negative or zero-distance buffer of lines and points is always an empty IPolygonal.

Exceptions

TopologyException

If a robustness error occurs

See Also

Buffer(double, int)

Computes a buffer region around this Geometry having the given width and with a specified accuracy of approximation for circular arcs. The buffer of a Geometry is the Minkowski sum of the Geometry with a disc of radius distance. Curves in the buffer polygon are approximated with line segments. This method allows specifying the accuracy of that approximation.

public Geometry Buffer(double distance, int quadrantSegments)

Parameters

distance double

The width of the buffer (may be positive, negative or 0), interpreted according to the PrecisionModel of the Geometry.

quadrantSegments int

The number of segments to use to approximate a quadrant of a circle.

Returns

Geometry

a polygonal geometry representing the buffer region (which may be empty)

Remarks

Mathematically-exact buffer area boundaries can contain circular arcs. To represent these arcs using linear geometry they must be approximated with line segments. The quadrantSegments argument allows controlling the accuracy of the approximation by specifying the number of line segments used to represent a quadrant of a circle

The buffer operation always returns a polygonal result. The negative or zero-distance buffer of lines and points is always an empty IPolygonal. This is also the result for the buffers of degenerate (zero-area) polygons.

Exceptions

TopologyException

If a robustness error occurs

See Also

Buffer(double, int, EndCapStyle)

Computes a buffer region around this Geometry having the given width and with a specified number of segments used to approximate curves. The buffer of a Geometry is the Minkowski sum of the Geometry with a disc of radius distance. Curves in the buffer polygon are approximated with line segments. This method allows specifying the accuracy of that approximation.

public Geometry Buffer(double distance, int quadrantSegments, EndCapStyle endCapStyle)

Parameters

distance double

The width of the buffer, interpreted according to the PrecisionModel of the Geometry.

quadrantSegments int

The number of segments to use to approximate a quadrant of a circle.

endCapStyle EndCapStyle

Cap Style to use for compute buffer.

Returns

Geometry

a polygonal geometry representing the buffer region (which may be empty)

Remarks

Mathematically-exact buffer area boundaries can contain circular arcs. To represent these arcs using linear geometry they must be approximated with line segments. The quadrantSegments argument allows controlling the accuracy of the approximation by specifying the number of line segments used to represent a quadrant of a circle

The end cap style specifies the buffer geometry that will be created at the ends of linestrings. The styles provided are:

  • Round - (default) a semi-circle
  • Flat - a straight line perpendicular to the end segment
  • Square - a half-square

The buffer operation always returns a polygonal result. The negative or zero-distance buffer of lines and points is always an empty IPolygonal. This is also the result for the buffers of degenerate (zero-area) polygons.

Exceptions

TopologyException

If a robustness error occurs

See Also

CheckNotGeometryCollection(Geometry)

Throws an exception if g's type is a GeometryCollection. (Its subclasses do not trigger an exception).

protected static void CheckNotGeometryCollection(Geometry g)

Parameters

g Geometry

The Geometry to check.

Exceptions

ArgumentException

if g is a GeometryCollection, but not one of its subclasses.

Compare(List<Geometry>, List<Geometry>)

Returns the first non-zero result of CompareTo encountered as the two Collections are iterated over. If, by the time one of the iterations is complete, no non-zero result has been encountered, returns 0 if the other iteration is also complete. If b completes before a, a positive number is returned; if a before b, a negative number.

protected static int Compare(List<Geometry> a, List<Geometry> b)

Parameters

a List<Geometry>

A Collection of IComparables.

b List<Geometry>

A Collection of IComparables.

Returns

int

The first non-zero compareTo result, if any; otherwise, zero.

CompareTo(Geometry)

Returns whether this Geometry is greater than, equal to, or less than another Geometry.

public int CompareTo(Geometry geom)

Parameters

geom Geometry

A Geometry with which to compare this Geometry

Returns

int

A positive number, 0, or a negative number, depending on whether this object is greater than, equal to, or less than o, as defined in "Normal Form For Geometry" in the NTS Technical Specifications.

Remarks

If their classes are different, they are compared using the following ordering:

  • Point (lowest),
  • MultiPoint,
  • LineString,
  • LinearRing,
  • MultiLineString,
  • Polygon,
  • MultiPolygon,
  • GeometryCollection (highest).
If the two Geometrys have the same class, their first elements are compared. If those are the same, the second elements are compared, etc.

CompareTo(object)

Returns whether this Geometry is greater than, equal to, or less than another Geometry.

public int CompareTo(object o)

Parameters

o object

A Geometry with which to compare this Geometry

Returns

int

A positive number, 0, or a negative number, depending on whether this object is greater than, equal to, or less than o, as defined in "Normal Form For Geometry" in the NTS Technical Specifications.

Remarks

If their classes are different, they are compared using the following ordering:

  • Point (lowest),
  • MultiPoint,
  • LineString,
  • LinearRing,
  • MultiLineString,
  • Polygon,
  • MultiPolygon,
  • GeometryCollection (highest).
If the two Geometrys have the same class, their first elements are compared. If those are the same, the second elements are compared, etc.

CompareTo(object, IComparer<CoordinateSequence>)

Returns whether this Geometry is greater than, equal to, or less than another Geometry, using the given .

public int CompareTo(object o, IComparer<CoordinateSequence> comp)

Parameters

o object

A Geometry with which to compare this Geometry

comp IComparer<CoordinateSequence>

A IComparer<CoordinateSequence>

Returns

int

A positive number, 0, or a negative number, depending on whether this object is greater than, equal to, or less than o, as defined in "Normal Form For Geometry" in the NTS Technical Specifications.

Remarks

If their classes are different, they are compared using the following ordering:

  • Point (lowest),
  • MultiPoint,
  • LineString,
  • LinearRing,
  • MultiLineString,
  • Polygon,
  • MultiPolygon,
  • GeometryCollection (highest).
If the two Geometrys have the same class, their first elements are compared. If those are the same, the second elements are compared, etc.

CompareToSameClass(object)

Returns whether this Geometry is greater than, equal to, or less than another Geometry having the same class.

protected abstract int CompareToSameClass(object o)

Parameters

o object

A Geometry having the same class as this Geometry.

Returns

int

A positive number, 0, or a negative number, depending on whether this object is greater than, equal to, or less than o, as defined in "Normal Form For Geometry" in the NTS Technical Specifications.

CompareToSameClass(object, IComparer<CoordinateSequence>)

Returns whether this Geometry is greater than, equal to, or less than another Geometry of the same class. using the given IComparer<T>.

protected abstract int CompareToSameClass(object o, IComparer<CoordinateSequence> comp)

Parameters

o object

A Geometry having the same class as this Geometry

comp IComparer<CoordinateSequence>

The comparer

Returns

int

A positive number, 0, or a negative number, depending on whether this object is greater than, equal to, or less than o, as defined in "Normal Form For Geometry" in the JTS Technical Specifications

ComputeEnvelopeInternal()

Returns the minimum and maximum x and y values in this Geometry, or a null Envelope if this Geometry is empty. Unlike EnvelopeInternal, this method calculates the Envelope each time it is called; EnvelopeInternal caches the result of this method.

protected abstract Envelope ComputeEnvelopeInternal()

Returns

Envelope

This Geometrys bounding box; if the Geometry is empty, Envelope.IsNull will return true.

Contains(Geometry)

Tests whether this geometry contains the argument geometry.

public virtual bool Contains(Geometry g)

Parameters

g Geometry

the Geometry with which to compare this Geometry

Returns

bool

true if this Geometry contains g

Remarks

The Contains predicate has the following equivalent definitions:

  • Every point of the other geometry is a point of this geometry, and the interiors of the two geometries have at least one point in common.
  • The DE-9IM Intersection Matrix for the two geometries matches the pattern [T*****FF*]
  • g.within(this)
    (Contains is the converse of Within(Geometry))

An implication of the definition is that "Geometries do not contain their boundary". In other words, if a geometry A is a subset of the points in the boundary of a geometry B, B.Contains(A) == false. (As a concrete example, take A to be a LineString which lies in the boundary of a Polygon B.) For a predicate with similar behaviour but avoiding this subtle limitation, see Covers(Geometry).

ConvexHull()

Returns the smallest convex Polygon that contains all the points in the Geometry. This obviously applies only to Geometry s which contain 3 or more points.

public virtual Geometry ConvexHull()

Returns

Geometry

the minimum-area convex polygon containing this Geometry's points.

Copy()

Creates a deep copy of this Geometry object. Coordinate sequences contained in it are copied. All instance fields are copied (i.e. the SRID, EnvelopeInternal and UserData).

public Geometry Copy()

Returns

Geometry

A deep copy of this geometry

Remarks

NOTE: The UserData object reference (if present) is copied, but the value itself is not copied. If a deep copy is required this must be performed by the caller.

CopyInternal()

An internal method to copy subclass-specific geometry data.

protected abstract Geometry CopyInternal()

Returns

Geometry

A copy of the target geometry object.

CoveredBy(Geometry)

Tests whether this geometry is covered by the specified geometry.

public bool CoveredBy(Geometry g)

Parameters

g Geometry

the Geometry with which to compare this Geometry

Returns

bool

true if this Geometry is covered by g

Remarks

The CoveredBy predicate has the following equivalent definitions:

  • Every point of this geometry is a point of the other geometry.
  • The DE-9IM Intersection Matrix for the two geometries matches at least one of the following patterns:
    • [T*F**F***]
    • [*TF**F***]
    • [**FT*F***]
    • [**F*TF***]
  • g.Covers(this) == true
    (CoveredBy is the converse of Covers(Geometry))
If either geometry is empty, the value of this predicate is false.

This predicate is similar to Within(Geometry), but is more inclusive (i.e. returns true for more cases).

See Also

Covers(Geometry)

Tests whether this geometry covers the argument geometry

public virtual bool Covers(Geometry g)

Parameters

g Geometry

The Geometry with which to compare this Geometry

Returns

bool

true if this Geometry covers g

Remarks

The covers predicate has the following equivalent definitions:

  • Every point of the other geometry is a point of this geometry.
  • The DE-9IM Intersection Matrix for the two geometries matches at least one of the following patterns:
    • [T*****FF*] or
    • [*T****FF*] or
    • [***T**FF*] or
    • [****T*FF*]
  • g.CoveredBy(this) == true
    (covers is the converse of CoveredBy(Geometry))
If either geometry is empty, the value of this predicate is false.

This predicate is similar to Contains(Geometry), but is more inclusive (i.e. returns true for more cases). In particular, unlike Contains it does not distinguish between points in the boundary and in the interior of geometries. For most situations, Covers should be used in preference to Contains. As an added benefit, Covers is more amenable to optimization, and hence should be more performant.

See Also

CreateArray(CoordinateSequence, Ordinate) 

protected static double[] CreateArray(CoordinateSequence sequence, Ordinate ordinate)

Parameters

sequence CoordinateSequence
ordinate Ordinate

Returns

double[]

CreateArray(int, double) 

protected static double[] CreateArray(int size, double value)

Parameters

size int
value double

Returns

double[]

Crosses(Geometry)

Tests whether this geometry crosses the specified geometry.

public virtual bool Crosses(Geometry g)

Parameters

g Geometry

The Geometry with which to compare this Geometry

Returns

bool

true if the two Geometrys cross.

Remarks

The Crosses predicate has the following equivalent definitions:

  • The geometries have some but not all interior points in common.
  • The DE-9IM Intersection Matrix for the two geometries matches one of the following patterns:
    CodeDescription
    [T*T******]for P/L, P/A, and L/A situations
    [T*****T**]for L/P, A/P, and A/L situations)
    [0********]for L/L situations
For the A/A and P/P situations this predicate returns false.

The SFS defined this predicate only for P/L, P/A, L/L, and L/A situations. To make the relation symmetric, NTS extends the definition to apply to L/P, A/P and A/L situations as well.

Difference(Geometry)

Computes a Geometry representing the closure of the point-set of the points contained in this Geometry that are not contained in the other Geometry.

If the result is empty, it is an atomic geometry with the dimension of the left-hand input.

Non-empty GeometryCollection arguments are not supported. 
public Geometry Difference(Geometry other)

Parameters

other Geometry

The Geometry with which to compute the difference.

Returns

Geometry

A Geometry representing the point-set difference of this Geometry with other.

Exceptions

ArgumentException

if the argument has a factory with a different GeometryOverlay object assigned

Disjoint(Geometry)

Tests whether this geometry is disjoint from the argument geometry.

public bool Disjoint(Geometry g)

Parameters

g Geometry

The Geometry with which to compare this Geometry.

Returns

bool

true if the two Geometrys are disjoint.

Remarks

The Disjoint predicate has the following equivalent definitions:

  • The DE-9IM intersection matrix for the two geometries matches FF*FF****.
  • !g.intersects(this) == true
    (Disjoint is the inverse of Intersects)

Distance(Geometry)

Returns the minimum distance between this Geometry and another Geometry g.

public virtual double Distance(Geometry g)

Parameters

g Geometry

The Geometry from which to compute the distance.

Returns

double

The distance between the geometries

Exceptions

ArgumentException

if g is null

Equal(Coordinate, Coordinate, double) 

[Obsolete("Will be removed in a future version")]
protected static bool Equal(Coordinate a, Coordinate b, double tolerance)

Parameters

a Coordinate
b Coordinate
tolerance double

Returns

bool

Equals(Geometry)

Tests whether this geometry is topologically equal to the argument geometry.

This method is included for backward compatibility reasons. It has been superseded by the EqualsTopologically(Geometry) method, which has been named to clearly denote its functionality.

This method should NOT be confused with the method Equals(object), which implements an exact equality comparison. 
public bool Equals(Geometry g)

Parameters

g Geometry

The Geometry with which to compare this Geometry

Returns

bool

true if the two Geometrys are topologically equal.

See Also

Equals(object)

Tests whether this geometry is structurally and numerically equal to a given Object.

public override bool Equals(object o)

Parameters

o object

The object to compare

Returns

bool

true if this geometry is exactly equal to the argument

Remarks

If the argument Object is not a Geometry, the result is false. Otherwise, the result is computed using EqualsExact(Geometry).

This method is provided to fulfill the Java contract for value-based object equality. In conjunction with GetHashCode() it provides semantics which are most useful for using Geometrys as keys and values in Java collections.

Note that to produce the expected result the input geometries should be in normal form. It is the caller's responsibility to perform this where required (using Normalized() or Normalize() as appropriate).
See Also

EqualsExact(Geometry)

Returns true if the two Geometrys are exactly equal. Two Geometries are exactly equal if:

  • they have the same class,
  • they have the same values of Coordinates in their internal Coordinate lists, in exactly the same order.
This provides a stricter test of equality than EqualsTopologically(Geometry), which is more useful in certain situations (such as using geometries as keys in collections).

This method does not test the values of the GeometryFactory, the SRID, or the UserData fields.

To properly test equality between different geometries, it is usually necessary to Normalize() them first. 
public bool EqualsExact(Geometry other)

Parameters

other Geometry

The Geometry with which to compare this Geometry.

Returns

bool

true if this and the other Geometry have identical structure and point values.

EqualsExact(Geometry, double)

Returns true if the two Geometrys are exactly equal, up to a specified tolerance. Two Geometries are exactly within a tolerance equal if:

  • they have the same class,
  • they have the same values of Coordinates, within the given tolerance distance, in their internal Coordinate lists, in exactly the same order.
This method does not test the values of the GeometryFactory, the SRID, or the UserData fields.

To properly test equality between different geometries, it is usually necessary to Normalize() them first. 
public abstract bool EqualsExact(Geometry other, double tolerance)

Parameters

other Geometry

The Geometry with which to compare this Geometry have identical structure and point values, up to the distance tolerance.

tolerance double

Distance at or below which two Coordinates will be considered equal.

Returns

bool

true if this and the other Geometry are of the same class and have equal internal data.

See Also

EqualsNormalized(Geometry)

Tests whether two geometries are exactly equal in their normalized forms. This is a convenience method which creates normalized versions of both geometries before computing EqualsExact(Geometry).

This method is relatively expensive to compute. For maximum performance, the client should instead perform normalization on the individual geometries at an appropriate point during processing. 

public bool EqualsNormalized(Geometry g)

Parameters

g Geometry

A geometry

Returns

bool

true if the input geometries are exactly equal in their normalized form

See Also

EqualsTopologically(Geometry)

Tests whether this geometry is topologically equal to the argument geometry as defined by the SFS Equals predicate.

public virtual bool EqualsTopologically(Geometry g)

Parameters

g Geometry

the Geometry with which to compare this Geometry

Returns

bool

true if the two Geometrys are topologically equal

Remarks

The SFS equals predicate has the following equivalent definitions:

  • The two geometries have at least one point in common, and no point of either geometry lies in the exterior of the other geometry.
  • The DE-9IM Intersection Matrix for the two geometries matches the pattern T*F**FFF* 
    T*F
**F
FF*
Note that this method computes topologically equality. For structural equality, see {@link #equalsExact(Geometry)}.

GeometryChanged()

Notifies this geometry that its coordinates have been changed by an external party (for example, via a ICoordinateFilter).

public void GeometryChanged()

Remarks

When this method is called the geometry will flush and/or update any derived information it has cached (such as its Envelope ). The operation is applied to all component Geometries.

GeometryChangedAction()

Notifies this Geometry that its Coordinates have been changed by an external party. When GeometryChanged is called, this method will be called for this Geometry and its component Geometries.

public void GeometryChangedAction()

GetGeometryN(int)

Returns an element Geometry from a GeometryCollection, or this, if the geometry is not a collection.

public virtual Geometry GetGeometryN(int n)

Parameters

n int

The index of the geometry element.

Returns

Geometry

The n'th geometry contained in this geometry.

GetHashCode()

Gets a hash code for the Geometry.

public override int GetHashCode()

Returns

int

An integer value suitable for use as a hashcode

GetOrdinates(Ordinate)

Gets an array of double ordinate values

public abstract double[] GetOrdinates(Ordinate ordinate)

Parameters

ordinate Ordinate

The ordinate index

Returns

double[]

An array of ordinate values

HasNonEmptyElements(Geometry[])

Returns true if the array contains any non-empty Geometrys.

protected static bool HasNonEmptyElements(Geometry[] geometries)

Parameters

geometries Geometry[]

an array of Geometrys; no elements may be null

Returns

bool

true if any of the Geometrys IsEmpty methods return false.

HasNullElements(object[])

Returns true if the array contains any null elements.

[Obsolete("Use HasNullElements<T>")]
public static bool HasNullElements(object[] array)

Parameters

array object[]

an array to validate.

Returns

bool

true if any of arrays elements are null.

HasNullElements<T>(IEnumerable<T>)

Returns true if the array contains any null elements.

public static bool HasNullElements<T>(IEnumerable<T> array) where T : class

Parameters

array IEnumerable<T>

an array to validate.

Returns

bool

true if any of arrays elements are null.

Type Parameters

T

Intersection(Geometry)

Computes a Geometry representing the point-set which is common to both this Geometry and the other Geometry.

The intersection of two geometries of different dimension produces a result geometry of dimension less than or equal to the minimum dimension of the input geometries. The result geometry may be a heterogeneous GeometryCollection. If the result is empty, it is an atomic geometry with the dimension of the lowest input dimension.

Intersection of GeometryCollections is supported only for homogeneous collection types.

Non-empty heterogeneous GeometryCollection arguments are not supported. 
public Geometry Intersection(Geometry other)

Parameters

other Geometry

The Geometry with which to compute the intersection.

Returns

Geometry

A geometry representing the point-set common to the two Geometrys.

Exceptions

TopologyException

if a robustness error occurs.

ArgumentException

if the argument is a non-empty heterogeneous GeometryCollection

ArgumentException

if the argument has a factory with a different GeometryOverlay object assigned

Intersects(Geometry)

Tests whether this geometry intersects the argument geometry.

public virtual bool Intersects(Geometry g)

Parameters

g Geometry

The Geometry with which to compare this Geometry.

Returns

bool

true if the two Geometrys intersect.

Remarks

The Intersects predicate has the following equivalent definitions:

  • The two geometries have at least one point in common
  • The DE-9IM Intersection Matrix for the two geometries matches
    [T********] or
    [*T*******] or
    [***T*****] or
    [****T****]
  • !g.disjoint(this)
    (Intersects is the inverse of Disjoint)

IsEquivalentClass(Geometry)

Returns whether the two Geometrys are equal, from the point of view of the EqualsExact method. Called by EqualsExact . In general, two Geometry classes are considered to be "equivalent" only if they are the same class. An exception is LineString , which is considered to be equivalent to its subclasses.

protected virtual bool IsEquivalentClass(Geometry other)

Parameters

other Geometry

The Geometry with which to compare this Geometry for equality.

Returns

bool

true if the classes of the two Geometry s are considered to be equal by the equalsExact method.

IsWithinDistance(Geometry, double)

Tests whether the distance from this Geometry to another is less than or equal to a specified value.

public virtual bool IsWithinDistance(Geometry geom, double distance)

Parameters

geom Geometry

the Geometry to check the distance to.

distance double

the distance value to compare.

Returns

bool

true if the geometries are less than distance apart.

Normalize()

Converts this Geometry to normal form (or canonical form ).

public abstract void Normalize()

Remarks

Normal form is a unique representation for Geometrys. It can be used to test whether two Geometrys are equal in a way that is independent of the ordering of the coordinates within them. Normal form equality is a stronger condition than topological equality, but weaker than pointwise equality.

The definitions for normal form use the standard lexicographical ordering for coordinates. "Sorted in order of coordinates" means the obvious extension of this ordering to sequences of coordinates.

NOTE that this method mutates the value of this geometry in-place. If this is not safe and/or wanted, the geometry should be cloned prior to normalization.

Normalized()

Creates a new Geometry which is a normalized copy of this Geometry.

public Geometry Normalized()

Returns

Geometry

A normalized copy of this geometry.

See Also

Overlaps(Geometry)

Tests whether this geometry overlaps the specified geometry.

public virtual bool Overlaps(Geometry g)

Parameters

g Geometry

The Geometry with which to compare this Geometry.

Returns

bool

true if the two Geometrys overlap. For this function to return true, the Geometry s must be two points, two curves or two surfaces.

Remarks

The Overlaps predicate has the following equivalent definitions:

  • The geometries have at least one point each not shared by the other (or equivalently neither covers the other), they have the same dimension, and the intersection of the interiors of the two geometries has the same dimension as the geometries themselves.
  • The DE-9IM Intersection Matrix for the two geometries matches [T*T***T**] (for two points or two surfaces) or [1*T***T**] (for two curves)
If the geometries are of different dimension this predicate returns false.

Relate(Geometry)

Returns the DE-9IM intersection matrix for the two Geometrys.

public virtual IntersectionMatrix Relate(Geometry g)

Parameters

g Geometry

The Geometry with which to compare this Geometry

Returns

IntersectionMatrix

A matrix describing the intersections of the interiors, boundaries and exteriors of the two Geometrys.

Relate(Geometry, string)

Tests whether the elements in the DE-9IM IntersectionMatrix for the two Geometrys match the elements in intersectionPattern.

public virtual bool Relate(Geometry g, string intersectionPattern)

Parameters

g Geometry

the Geometry with which to compare this Geometry

intersectionPattern string

the pattern against which to check the intersection matrix for the two Geometrys

Returns

bool

true if the DE-9IM intersection matrix for the two Geometrys match intersectionPattern

Remarks

The pattern is a 9-character string, with symbols drawn from the following set:

0(dimension 0)
1(dimension 1)
2(dimension 2)
T( matches 0, 1 or 2)
F( matches FALSE)
*( matches any value)
For more information on the DE-9IM, see the OpenGIS Simple Features Specification.
See Also

Reverse()

Computes a new geometry which has all component coordinate sequences in reverse order (opposite orientation) to this one.

public virtual Geometry Reverse()

Returns

Geometry

A reversed geometry

Remarks

Don't override this function, implement ReverseInternal().

ReverseInternal()

The actual implementation of the Reverse() function

protected virtual Geometry ReverseInternal()

Returns

Geometry

A reversed geometry

Remarks

In JTS this function is abstract, but that would break binary compatibility of current version.

SymmetricDifference(Geometry)

Computes a Geometry representing the closure of the point-set which is the union of the points in this Geometry which are not contained in the other Geometry, with the points in the other Geometry not contained in this Geometry. If the result is empty, it is an atomic geometry with the dimension of the highest input dimension.

Non-empty GeometryCollection arguments are not supported. 
public Geometry SymmetricDifference(Geometry other)

Parameters

other Geometry

The Geometry with which to compute the symmetric difference.

Returns

Geometry

a Geometry representing the point-set symmetric difference of this Geometry with other.

Exceptions

ArgumentException

if the argument has a factory with a different GeometryOverlay object assigned

ToBinary()

Returns the Well-known Binary representation of this Geometry. For a definition of the Well-known Binary format, see the OpenGIS Simple Features Specification.

public byte[] ToBinary()

Returns

byte[]

The Well-known Binary representation of this Geometry.

ToGMLFeature()

Returns the feature representation as GML 2.1.1 XML document. This XML document is based on Geometry.xsd schema. NO features or XLink are implemented here!

public XmlReader ToGMLFeature()

Returns

XmlReader

ToString()

Returns the Well-known Text representation of this Geometry. For a definition of the Well-known Text format, see the OpenGIS Simple Features Specification.

public override string ToString()

Returns

string

The Well-known Text representation of this Geometry.

ToText()

Returns the Well-known Text representation of this Geometry. For a definition of the Well-known Text format, see the OpenGIS Simple Features Specification.

public string ToText()

Returns

string

The Well-known Text representation of this Geometry.

Touches(Geometry)

Tests whether this geometry touches the argument geometry

public virtual bool Touches(Geometry g)

Parameters

g Geometry

The Geometry with which to compare this Geometry.

Returns

bool

true if the two Geometrys touch; Returns false if both Geometrys are points.

Remarks

The Touches predicate has the following equivalent definitions:

  • The geometries have at least one point in common, but their interiors do not intersect
  • The DE-9IM Intersection Matrix for the two geometries matches at least one of the following patterns
    • FT*******,
    • F**T***** or
    • F***T****.
If both geometries have dimension 0, the predicate returns false, since points have only interiors. This predicate is symmetric.

Union()

Computes the union of all the elements of this geometry.

public Geometry Union()

Returns

Geometry

Remarks

This method supports GeometryCollections (which the other overlay operations currently do not).

Exceptions

TopologyException

Thrown if a robustness error occurs

Union(Geometry)

Computes a Geometry representing the point-set which is contained in both this Geometry and the other Geometry.

public Geometry Union(Geometry other)

Parameters

other Geometry

the Geometry with which to compute the union

Returns

Geometry

A point-set combining the points of this Geometry and the points of other

Remarks

The method may be used on arguments of different dimension, but it does not support GeometryCollection arguments.

The union of two geometries of different dimension produces a result geometry of dimension equal to the maximum dimension of the input geometries. The result geometry may be a heterogeneous GeometryCollection. If the result is empty, it is an atomic geometry with the dimension of the highest input dimension.

Unioning LineStrings has the effect of noding and dissolving the input linework. In this context "noding" means that there will be a node or endpoint in the result for every endpoint or line segment crossing in the input. "Dissolving" means that any duplicate (i.e. coincident) line segments or portions of line segments will be reduced to a single line segment in the result. If merged linework is required, the LineMerger class can be used.

Non-empty GeometryCollection arguments are not supported.

Exceptions

TopologyException

Thrown if a robustness error occurs

ArgumentException

Thrown if either input is a non-empty GeometryCollection

ArgumentException

if the argument has a factory with a different GeometryOverlay object assigned

See Also

Within(Geometry)

Tests whether this geometry is within the specified geometry.

public bool Within(Geometry g)

Parameters

g Geometry

The Geometry with which to compare this Geometry.

Returns

bool

true if this Geometry is within other.

Remarks

The within predicate has the following equivalent definitions:

  • Every point of this geometry is a point of the other geometry, and the interiors of the two geometries have at least one point in common.
  • The DE-9IM Intersection Matrix for the two geometries matches [T*F**F***]
  • g.contains(this) == true
    (Within is the converse of Contains(Geometry))

An implication of the definition is that "The boundary of a geometry is not within the Polygon". In other words, if a geometry A is a subset of the points in the boundary of a geometry B, A.within(B) == false (As a concrete example, take A to be a LineString which lies in the boundary of a Polygon B.) For a predicate with similar behaviour but avoiding this subtle limitation, see CoveredBy(Geometry).

Operators

operator ==(Geometry, Geometry) 

public static bool operator ==(Geometry obj1, Geometry obj2)

Parameters

obj1 Geometry
obj2 Geometry

Returns

bool

operator !=(Geometry, Geometry) 

public static bool operator !=(Geometry obj1, Geometry obj2)

Parameters

obj1 Geometry
obj2 Geometry

Returns

bool