Specifies the precision model of the Coordinate in a Geometry. More...

#include <geos.h>

Public Types
enum	Type { FIXED, FLOATING, FLOATING_SINGLE }
	The types of Precision Model which GEOS supports. More...

Public Member Functions
	PrecisionModel (void)
	Creates a PrecisionModel with a default precision of FLOATING. More...

	PrecisionModel (Type nModelType)

	PrecisionModel (double newScale, double newOffsetX, double newOffsetY)
	Creates a `PrecisionModel` with Fixed precision. More...

	PrecisionModel (double newScale)
	Creates a PrecisionModel with Fixed precision. More...

double	makePrecise (double val) const
	Rounds a numeric value to the PrecisionModel grid. More...

void	makePrecise (Coordinate &coord) const
	Rounds the given Coordinate to the PrecisionModel grid. More...

void	makePrecise (Coordinate *coord) const

bool	isFloating () const

int	getMaximumSignificantDigits () const
	Returns the maximum number of significant digits provided by this precision model. More...

Type	getType () const

double	getScale () const
	Returns the multiplying factor used to obtain a precise coordinate. More...

double	getOffsetX () const

double	getOffsetY () const

std::string	toString () const

int	compareTo (const PrecisionModel *other) const
	Compares this PrecisionModel object with the specified object for order. More...

Static Public Attributes
static const double	maximumPreciseValue

Private Member Functions
void	setScale (double newScale)
	Sets the multiplying factor used to obtain a precise coordinate. More...

Private Attributes
Type	modelType

double	scale

Friends
class	io::Unload

Detailed Description

Specifies the precision model of the Coordinate 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:

FLOATING - represents full double precision floating point. This is the default precision model used in JTS
FLOATING_SINGLE - represents single precision floating point.
FIXED - represents a model with a fixed number of decimal places. A Fixed Precision Model is specified by a scale factor. The scale factor specifies the grid which numbers are rounded to. Input coordinates are mapped to fixed coordinates according to the following equations:
- jtsPt.x = round( inputPt.x * scale ) / scale
- jtsPt.y = round( inputPt.y * scale ) / scale

For example, to specify 3 decimal places of precision, use a scale factor of 1000. To specify -3 decimal places of precision (i.e. rounding to the nearest 1000), use a scale factor of 0.001.

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.

Definition at line 87 of file PrecisionModel.h.

Member Enumeration Documentation

enum geos::geom::PrecisionModel::Type

The types of Precision Model which GEOS supports.

Enumerator
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	Floating precision corresponds to the standard Java double-precision floating-point representation, which is based on the IEEE-754 standard
FLOATING_SINGLE	Floating single precision corresponds to the standard Java single-precision floating-point representation, which is based on the IEEE-754 standard

Definition at line 93 of file PrecisionModel.h.

Constructor & Destructor Documentation

geos::geom::PrecisionModel::PrecisionModel ( void )

Creates a PrecisionModel with a default precision of FLOATING.

geos::geom::PrecisionModel::PrecisionModel ( Type nModelType )

Creates a PrecisionModel specifying an explicit precision model type.

If the model type is FIXED the scale factor will default to 1.

Parameters

nModelType the type of the precision model

geos::geom::PrecisionModel::PrecisionModel	(	double	newScale,
		double	newOffsetX,
		double	newOffsetY
	)

Creates a PrecisionModel with Fixed precision.

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

Parameters

newScale	amount by which to multiply a coordinate after subtracting the offset, to obtain a precise coordinate
newOffsetX	not used.
newOffsetY	not used.

Deprecated:: offsets are no longer supported, since internal representation is rounded floating point

geos::geom::PrecisionModel::PrecisionModel ( double newScale )

Creates a PrecisionModel with Fixed precision.

Fixed-precision coordinates are represented as precise internal coordinates which are rounded to the grid defined by the scale factor.

Parameters

newScale amount by which to multiply a coordinate after subtracting the offset, to obtain a precise coordinate

Member Function Documentation

int geos::geom::PrecisionModel::compareTo ( const PrecisionModel * other ) const

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 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.

Parameters

other 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.

int geos::geom::PrecisionModel::getMaximumSignificantDigits ( ) const

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

double geos::geom::PrecisionModel::getOffsetX ( ) const

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

Deprecated:: Offsets are no longer used

double geos::geom::PrecisionModel::getOffsetY ( ) const

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

Deprecated:: Offsets are no longer used

double geos::geom::PrecisionModel::getScale ( ) const

Returns the multiplying factor used to obtain a precise coordinate.

Type geos::geom::PrecisionModel::getType ( ) const

Gets the type of this PrecisionModel

Returns: the type of this PrecisionModel

bool geos::geom::PrecisionModel::isFloating ( ) const

Tests whether the precision model supports floating point

Returns: true if the precision model supports floating point

double geos::geom::PrecisionModel::makePrecise ( double val ) const

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.

Referenced by geos::operation::buffer::OffsetSegmentString::addPt().

Here is the caller graph for this function:

void geos::geom::PrecisionModel::makePrecise ( Coordinate & coord ) const

Rounds the given Coordinate to the PrecisionModel grid.

void geos::geom::PrecisionModel::makePrecise ( Coordinate * coord ) const

void geos::geom::PrecisionModel::setScale ( double newScale )

private

Sets the multiplying factor used to obtain a precise coordinate.

This method is private because PrecisionModel is intended to be an immutable (value) type.

std::string geos::geom::PrecisionModel::toString ( ) const

Friends And Related Function Documentation

friend class io::Unload

friend

Definition at line 88 of file PrecisionModel.h.

Member Data Documentation

const double geos::geom::PrecisionModel::maximumPreciseValue

static

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.

Definition at line 166 of file PrecisionModel.h.

Type geos::geom::PrecisionModel::modelType

private

Definition at line 307 of file PrecisionModel.h.

double geos::geom::PrecisionModel::scale

private

Definition at line 309 of file PrecisionModel.h.

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

PrecisionModel.h

Public Types

Public Member Functions

Static Public Attributes

Private Member Functions

Private Attributes

Friends

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Friends And Related Function Documentation

Member Data Documentation