com.vividsolutions.jts.geom
Class PrecisionModel

java.lang.Object
  extended bycom.vividsolutions.jts.geom.PrecisionModel
All Implemented Interfaces:
java.lang.Comparable, java.io.Serializable

public class PrecisionModel
extends java.lang.Object
implements java.io.Serializable, java.lang.Comparable

Specifies the precision model of the Coordinates in a Geometry. In other words, specifies the grid of allowable points for all Geometrys.

The makePrecise method allows rounding a coordinate to a "precise" value; that is, one whose precision is known exactly.

Coordinates are assumed to be precise in geometries. That is, the coordinates are assumed to be rounded to the precision model given for the geometry. JTS input routines automatically round coordinates to the precision model before creating Geometries. All internal operations assume that coordinates are rounded to the precision model. Constructive methods (such as boolean operations) always round computed coordinates to the appropriate precision model.

Currently three types of precision model are supported:

Coordinates are represented internally as Java double-precision values. Since Java uses the IEEE-394 floating point standard, this provides 53 bits of precision. (Thus the maximum precisely representable integer is 9,007,199,254,740,992).

JTS methods currently do not handle inputs with different precision models.

Version:
1.7
See Also:
Serialized Form

Field Summary
static com.vividsolutions.jts.geom.PrecisionModel.Type FIXED
          Fixed Precision indicates that coordinates have a fixed number of decimal places.
static com.vividsolutions.jts.geom.PrecisionModel.Type FLOATING
          Floating precision corresponds to the standard Java double-precision floating-point representation, which is based on the IEEE-754 standard
static com.vividsolutions.jts.geom.PrecisionModel.Type FLOATING_SINGLE
          Floating single precision corresponds to the standard Java single-precision floating-point representation, which is based on the IEEE-754 standard
static double maximumPreciseValue
          The maximum precise value representable in a double.
 
Constructor Summary
PrecisionModel()
          Creates a PrecisionModel with a default precision of FLOATING.
PrecisionModel(double scale)
          Creates a PrecisionModel that specifies Fixed precision.
PrecisionModel(double scale, double offsetX, double offsetY)
          Deprecated. offsets are no longer supported, since internal representation is rounded floating point
PrecisionModel(com.vividsolutions.jts.geom.PrecisionModel.Type modelType)
          Creates a PrecisionModel that specifies an explicit precision model type.
PrecisionModel(PrecisionModel pm)
          Copy constructor to create a new PrecisionModel from an existing one.
 
Method Summary
 int compareTo(java.lang.Object o)
          Compares this PrecisionModel object with the specified object for order.
 boolean equals(java.lang.Object other)
           
 int getMaximumSignificantDigits()
          Returns the maximum number of significant digits provided by this precision model.
 double getOffsetX()
          Deprecated. Offsets are no longer used
 double getOffsetY()
          Deprecated. Offsets are no longer used
 double getScale()
          Returns the multiplying factor used to obtain a precise coordinate.
 com.vividsolutions.jts.geom.PrecisionModel.Type getType()
          Gets the type of this PrecisionModel
 boolean isFloating()
          Tests whether the precision model supports floating point
 void makePrecise(Coordinate coord)
          Rounds a Coordinate to the PrecisionModel grid.
 double makePrecise(double val)
          Rounds a numeric value to the PrecisionModel grid.
static PrecisionModel mostPrecise(PrecisionModel pm1, PrecisionModel pm2)
          Determines which of two PrecisionModels is the most precise (allows the greatest number of significant digits).
 Coordinate toExternal(Coordinate internal)
          Deprecated. no longer needed, since internal representation is same as external representation
 void toExternal(Coordinate internal, Coordinate external)
          Deprecated. no longer needed, since internal representation is same as external representation
 Coordinate toInternal(Coordinate external)
          Deprecated. use makePrecise instead
 void toInternal(Coordinate external, Coordinate internal)
          Deprecated. use makePrecise instead
 java.lang.String toString()
           
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

FIXED

public static final com.vividsolutions.jts.geom.PrecisionModel.Type FIXED
Fixed Precision indicates that coordinates have a fixed number of decimal places. The number of decimal places is determined by the log10 of the scale factor.


FLOATING

public static final com.vividsolutions.jts.geom.PrecisionModel.Type FLOATING
Floating precision corresponds to the standard Java double-precision floating-point representation, which is based on the IEEE-754 standard


FLOATING_SINGLE

public static final com.vividsolutions.jts.geom.PrecisionModel.Type FLOATING_SINGLE
Floating single precision corresponds to the standard Java single-precision floating-point representation, which is based on the IEEE-754 standard


maximumPreciseValue

public static final double maximumPreciseValue
The maximum precise value representable in a double. Since IEE754 double-precision numbers allow 53 bits of mantissa, the value is equal to 2^53 - 1. This provides almost 16 decimal digits of precision.

See Also:
Constant Field Values
Constructor Detail

PrecisionModel

public PrecisionModel()
Creates a PrecisionModel with a default precision of FLOATING.


PrecisionModel

public PrecisionModel(com.vividsolutions.jts.geom.PrecisionModel.Type modelType)
Creates a PrecisionModel that specifies an explicit precision model type. If the model type is FIXED the scale factor will default to 1.

Parameters:
modelType - the type of the precision model

PrecisionModel

public PrecisionModel(double scale,
                      double offsetX,
                      double offsetY)
Deprecated. offsets are no longer supported, since internal representation is rounded floating point

Creates a PrecisionModel that specifies Fixed precision. Fixed-precision coordinates are represented as precise internal coordinates, which are rounded to the grid defined by the scale factor.

Parameters:
scale - amount by which to multiply a coordinate after subtracting the offset, to obtain a precise coordinate
offsetX - not used.
offsetY - not used.

PrecisionModel

public PrecisionModel(double scale)
Creates a PrecisionModel that specifies Fixed precision. Fixed-precision coordinates are represented as precise internal coordinates, which are rounded to the grid defined by the scale factor.

Parameters:
scale - amount by which to multiply a coordinate after subtracting the offset, to obtain a precise coordinate

PrecisionModel

public PrecisionModel(PrecisionModel pm)
Copy constructor to create a new PrecisionModel from an existing one.

Method Detail

mostPrecise

public static PrecisionModel mostPrecise(PrecisionModel pm1,
                                         PrecisionModel pm2)
Determines which of two PrecisionModels is the most precise (allows the greatest number of significant digits).

Parameters:
pm1 - a PrecisionModel
pm2 - a PrecisionModel
Returns:
the PrecisionModel which is most precise

isFloating

public boolean isFloating()
Tests whether the precision model supports floating point

Returns:
true if the precision model supports floating point

getMaximumSignificantDigits

public int getMaximumSignificantDigits()
Returns the maximum number of significant digits provided by this precision model. Intended for use by routines which need to print out precise values.

Returns:
the maximum number of decimal places provided by this precision model

getScale

public double getScale()
Returns the multiplying factor used to obtain a precise coordinate. This method is private because PrecisionModel is intended to be an immutable (value) type.

Returns:
the amount by which to multiply a coordinate after subtracting the offset

getType

public com.vividsolutions.jts.geom.PrecisionModel.Type getType()
Gets the type of this PrecisionModel

Returns:
the type of this PrecisionModel

getOffsetX

public double getOffsetX()
Deprecated. Offsets are no longer used

Returns the x-offset used to obtain a precise coordinate.

Returns:
the amount by which to subtract the x-coordinate before multiplying by the scale

getOffsetY

public double getOffsetY()
Deprecated. Offsets are no longer used

Returns the y-offset used to obtain a precise coordinate.

Returns:
the amount by which to subtract the y-coordinate before multiplying by the scale

toInternal

public void toInternal(Coordinate external,
                       Coordinate internal)
Deprecated. use makePrecise instead

Sets internal to the precise representation of external.

Parameters:
external - the original coordinate
internal - the coordinate whose values will be changed to the precise representation of external

toInternal

public Coordinate toInternal(Coordinate external)
Deprecated. use makePrecise instead

Returns the precise representation of external.

Parameters:
external - the original coordinate
Returns:
the coordinate whose values will be changed to the precise representation of external

toExternal

public Coordinate toExternal(Coordinate internal)
Deprecated. no longer needed, since internal representation is same as external representation

Returns the external representation of internal.

Parameters:
internal - the original coordinate
Returns:
the coordinate whose values will be changed to the external representation of internal

toExternal

public void toExternal(Coordinate internal,
                       Coordinate external)
Deprecated. no longer needed, since internal representation is same as external representation

Sets external to the external representation of internal .

Parameters:
internal - the original coordinate
external - the coordinate whose values will be changed to the external representation of internal

makePrecise

public double makePrecise(double val)
Rounds a numeric value to the PrecisionModel grid. Asymmetric Arithmetic Rounding is used, to provide uniform rounding behaviour no matter where the number is on the number line.

Note: Java's Math#rint uses the "Banker's Rounding" algorithm, which is not suitable for precision operations elsewhere in JTS.


makePrecise

public void makePrecise(Coordinate coord)
Rounds a Coordinate to the PrecisionModel grid.


toString

public java.lang.String toString()

equals

public boolean equals(java.lang.Object other)

compareTo

public int compareTo(java.lang.Object o)
Compares this PrecisionModel object with the specified object for order. A PrecisionModel is greater than another if it provides greater precision. The comparison is based on the value returned by the {@link getMaximumSignificantDigits) method. This comparison is not strictly accurate when comparing floating precision models to fixed models; however, it is correct when both models are either floating or fixed.

Specified by:
compareTo in interface java.lang.Comparable
Parameters:
o - the PrecisionModel with which this PrecisionModel is being compared
Returns:
a negative integer, zero, or a positive integer as this PrecisionModel is less than, equal to, or greater than the specified PrecisionModel