Table of Contents

Class PrecisionModel

Namespace
NetTopologySuite.Geometries
Assembly
NetTopologySuite.dll

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.

public class PrecisionModel : IComparable, IComparable<PrecisionModel>
Inheritance
PrecisionModel
Implements
Inherited Members

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:
FloatingRepresents full double precision floating point. This is the default precision model used in NTS
FloatingSingleRepresents single precision floating point
FixedRepresents 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.

public PrecisionModel()

PrecisionModel(PrecisionModel)

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

public PrecisionModel(PrecisionModel pm)

Parameters

pm PrecisionModel

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.

public PrecisionModel(PrecisionModels modelType)

Parameters

modelType PrecisionModels

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. 
public PrecisionModel(double scale)

Parameters

scale double

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.

public const double MaximumPreciseValue = 9007199254740992

Field Value

double

Properties

Fixed

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

public static Lazy<PrecisionModel> Fixed { get; }

Property Value

Lazy<PrecisionModel>

A fixed precision model

Floating

Gets a value indicating a precision model with double precision.

public static Lazy<PrecisionModel> Floating { get; }

Property Value

Lazy<PrecisionModel>

A double precision model

FloatingSingle

Gets a value indicating a precision model with single precision.

public static Lazy<PrecisionModel> FloatingSingle { get; }

Property Value

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.

public double GridSize { get; }

Property Value

double

The grid size at a fixed precision scale.

IsFloating

Tests whether the precision model supports floating point.

public bool IsFloating { get; }

Property Value

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.

public int MaximumSignificantDigits { get; }

Property Value

int

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

PrecisionModelType

Gets the type of this PrecisionModel.

public PrecisionModels PrecisionModelType { get; }

Property Value

PrecisionModels

Scale

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

public double Scale { get; set; }

Property Value

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) 

public int CompareTo(PrecisionModel other)

Parameters

other PrecisionModel

Returns

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.

public int CompareTo(object o)

Parameters

o object

The PrecisionModel with which this PrecisionModel is being compared.

Returns

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) 

public bool Equals(PrecisionModel otherPrecisionModel)

Parameters

otherPrecisionModel PrecisionModel

Returns

bool

Equals(object) 

public override bool Equals(object other)

Parameters

other object

Returns

bool

GetHashCode() 

public override int GetHashCode()

Returns

int

MakePrecise(Coordinate)

Rounds a Coordinate to the PrecisionModel grid.

public void MakePrecise(Coordinate coord)

Parameters

coord Coordinate

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.

public double MakePrecise(double val)

Parameters

val double

Returns

double

Remarks

This method has no effect on NaN values

MostPrecise(PrecisionModel, PrecisionModel)

Determines which of two PrecisionModels is the most precise

public static PrecisionModel MostPrecise(PrecisionModel pm1, PrecisionModel pm2)

Parameters

pm1 PrecisionModel

A precision model

pm2 PrecisionModel

A precision model

Returns

PrecisionModel

The PrecisionModel which is most precise

ToString() 

public override string ToString()

Returns

string

Operators

operator ==(PrecisionModel, PrecisionModel) 

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

Parameters

obj1 PrecisionModel
obj2 PrecisionModel

Returns

bool

operator !=(PrecisionModel, PrecisionModel) 

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

Parameters

obj1 PrecisionModel
obj2 PrecisionModel

Returns

bool