Class PrecisionModel

Specifies the precision model of the Coordinates in a Geometry. In other words, specifies the grid of allowable points for a Geometry. A precision model may befloating (Floating or FloatingSingle), in which case normal floating-point value semantics apply.

Inheritance

object

PrecisionModel

Implements

IComparable

IComparable<PrecisionModel>

Inherited Members

object.Equals(object, object)

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

Namespace: NetTopologySuite.Geometries

Assembly: NetTopologySuite.dll

Syntax

[Serializable]
public class PrecisionModel : IComparable, IComparable<PrecisionModel>

Remarks

For a Fixed precision model the MakePrecise(Coordinate) 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.

All internal operations assume that coordinates are rounded to the precision model. Constructive methods (such as bool operations) always round computed coordinates to the appropriate precision model.
Three types of precision model are supported:

Floating	Represents full double precision floating point. This is the default precision model used in NTS
FloatingSingle	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 size of the grid which numbers are rounded to.

Input coordinates are mapped to fixed coordinates according to the following equations:

• jtsPt.X = Math.Round( inputPt.X * scale, MidPointRounding.AwayFromZero ) / scale )
• jtsPt.Y = Math.Round( inputPt.Y * scale, MidPointRounding.AwayFromZero ) / 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.

It is also supported to specify a precise grid size by providing it as a negative scale factor. This allows setting a precise grid size rather than using a fractional scale, which provides more accurate and robust rounding. For example, to specify rounding to the nearest 1000 use a scale factor of -1000.

Coordinates are represented internally as Java double-precision values. .NET uses the IEEE-394 floating point standard, which provides 53 bits of precision. (Thus the maximum precisely representable integer is 9,007,199,254,740,992 - or almost 16 decimal digits of precision).

Constructors

PrecisionModel()

Creates a PrecisionModel with a default precision of Floating.

Declaration

public PrecisionModel()

PrecisionModel(PrecisionModel)

Copy constructor to create a new PrecisionModel from an existing one.

Declaration

public PrecisionModel(PrecisionModel pm)

Parameters

Type	Name	Description
PrecisionModel	pm

PrecisionModel(PrecisionModels)

Creates a PrecisionModel that specifies an explicit precision model type. If the model type is Fixed the scale factor will default to 1.

Declaration

public PrecisionModel(PrecisionModels modelType)

Parameters

Type	Name	Description
PrecisionModels	modelType	The type of the precision model.

PrecisionModel(double)

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.

The provided scale may be negative, to specify an exact grid size. The scale is then computed as the reciprocal.

Declaration

public PrecisionModel(double scale)

Parameters

Type	Name	Description
double	scale	Amount by which to multiply a coordinate, to obtain a precise coordinate. Must be non-zero

Fields

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.

Declaration

public const double MaximumPreciseValue = 9007199254740992

Field Value

Type	Description
double

Properties

Fixed

Gets a value indicating a precision model with a scale of 1.

Declaration

public static Lazy<PrecisionModel> Fixed { get; }

Property Value

Type	Description
Lazy<PrecisionModel>	A fixed precision model

Floating

Gets a value indicating a precision model with double precision.

Declaration

public static Lazy<PrecisionModel> Floating { get; }

Property Value

Type	Description
Lazy<PrecisionModel>	A double precision model

FloatingSingle

Gets a value indicating a precision model with single precision.

Declaration

public static Lazy<PrecisionModel> FloatingSingle { get; }

Property Value

Type	Description
Lazy<PrecisionModel>	A single precision model

GridSize

Computes the grid size for a fixed precision model. This is equal to the reciprocal of the scale factor. If the grid size has been set explicity (via a negative scale factor) it will be returned.

Declaration

public double GridSize { get; }

Property Value

Type	Description
double	The grid size at a fixed precision scale.

IsFloating

Tests whether the precision model supports floating point.

Declaration

public bool IsFloating { get; }

Property Value

Type	Description
bool	true if the precision model supports floating point.

MaximumSignificantDigits

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

Declaration

public int MaximumSignificantDigits { get; }

Property Value

Type	Description
int	The maximum number of decimal places provided by this precision model.

PrecisionModelType

Gets the type of this PrecisionModel.

Declaration

public PrecisionModels PrecisionModelType { get; }

Property Value

Type	Description
PrecisionModels

Scale

Returns the scale factor used to specify a fixed precision model.

Declaration

public double Scale { get; set; }

Property Value

Type	Description
double	The scale factor for the fixed precision model

Remarks

The number of decimal places of precision is equal to the base-10 logarithm of the scale factor. Non-integral and negative scale factors are supported. Negative scale factors indicate that the places of precision is to the left of the decimal point.

Methods

CompareTo(PrecisionModel)

Declaration

public int CompareTo(PrecisionModel other)

Parameters

Type	Name	Description
PrecisionModel	other

Returns

Type	Description
int

CompareTo(object)

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.

Declaration

public int CompareTo(object o)

Parameters

Type	Name	Description
object	o	The PrecisionModel with which this PrecisionModel is being compared.

Returns

Type	Description
int	A negative integer, zero, or a positive integer as this PrecisionModel is less than, equal to, or greater than the specified PrecisionModel.

Equals(PrecisionModel)

Declaration

public bool Equals(PrecisionModel otherPrecisionModel)

Parameters

Type	Name	Description
PrecisionModel	otherPrecisionModel

Returns

Type	Description
bool

Equals(object)

Declaration

public override bool Equals(object other)

Parameters

Type	Name	Description
object	other

Returns

Type	Description
bool

Overrides

object.Equals(object)

GetHashCode()

Declaration

public override int GetHashCode()

Returns

Type	Description
int

Overrides

object.GetHashCode()

MakePrecise(Coordinate)

Rounds a Coordinate to the PrecisionModel grid.

Declaration

public void MakePrecise(Coordinate coord)

Parameters

Type	Name	Description
Coordinate	coord

MakePrecise(double)

Rounds a numeric value to the PrecisionModel grid. Symmetric Arithmetic Rounding is used, to provide uniform rounding behaviour no matter where the number is on the number line.

Declaration

public double MakePrecise(double val)

Parameters

Type	Name	Description
double	val

Returns

Type	Description
double

Remarks

This method has no effect on NaN values

MostPrecise(PrecisionModel, PrecisionModel)

Determines which of two PrecisionModels is the most precise

Declaration

public static PrecisionModel MostPrecise(PrecisionModel pm1, PrecisionModel pm2)

Parameters

Type	Name	Description
PrecisionModel	pm1	A precision model
PrecisionModel	pm2	A precision model

Returns

Type	Description
PrecisionModel	The PrecisionModel which is most precise

ToString()

Declaration

public override string ToString()

Returns

Type	Description
string

Overrides

object.ToString()

Operators

operator ==(PrecisionModel, PrecisionModel)

Declaration

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

Parameters

Type	Name	Description
PrecisionModel	obj1
PrecisionModel	obj2

Returns

Type	Description
bool

operator !=(PrecisionModel, PrecisionModel)

Declaration

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

Parameters

Type	Name	Description
PrecisionModel	obj1
PrecisionModel	obj2

Returns

Type	Description
bool

Implements

IComparable

IComparable<T>