Class PrecisionUtility

Functions for computing precision model scale factors that ensure robust geometry operations. In particular, these can be used to automatically determine appropriate scale factors for operations using limited-precision noding (such as OverlayNG).

WARNING: the inherentScale and robustScale functions can be very slow, due to the method used to determine number of decimal places of a number. These are not recommended for production use.

Inheritance

object

PrecisionUtility

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: NetTopologySuite.Operation.OverlayNG

Assembly: NetTopologySuite.dll

Syntax

public static class PrecisionUtility

Fields

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MAX_ROBUST_DP_DIGITS

A number of digits of precision which leaves some computational "headroom" to ensure robust evaluation of certain double-precision floating point geometric operations.

This value should be less than the maximum decimal precision of double-precision values (16).

Declaration

public static int MAX_ROBUST_DP_DIGITS

Field Value

Type	Description
int

Methods

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InherentScale(Geometry)

Computes the inherent scale of a geometry. The inherent scale is the scale factor for rounding which preserves all digits of precision (significant digits) present in the geometry ordinates.

This is the maximum inherent scale of all ordinate values in the geometry.

WARNING: this is very slow.

Declaration

public static double InherentScale(Geometry geom)

Parameters

Type	Name	Description
Geometry	geom	A geometry

Returns

Type	Description
double	The inherent scale factor in the geometry's ordinates

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InherentScale(Geometry, Geometry)

Computes the inherent scale of two geometries. The inherent scale is the scale factor for rounding which preserves all digits of precision (significant digits) present in the geometry ordinates.

This is the maximum inherent scale of all ordinate values in the geometries.

Declaration

public static double InherentScale(Geometry a, Geometry b)

Parameters

Type	Name	Description
Geometry	a	A geometry
Geometry	b	A geomety (which may be `null`)

Returns

Type	Description
double	The inherent scale factor in the geometries' ordinates

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InherentScale(double)

Computes the inherent scale of a number. The inherent scale is the scale factor for rounding which preserves all digits of precision (significant digits) present in the numeric value. In other words, it is the scale factor which does not change the numeric value when rounded:

num = round( num, inherentScale(num) )

Declaration

public static double InherentScale(double value)

Parameters

Type	Name	Description
double	value	A number

Returns

Type	Description
double	The inherent scale factor of the number

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RobustPM(Geometry)

Determines a precision model to use for robust overlay operations for one geometry. The precision scale factor is chosen to maximize output precision while avoiding round-off issues.

NOTE: this is a heuristic determination, so is not guaranteed to eliminate precision issues.

WARNING: this is very slow.

Declaration

public static PrecisionModel RobustPM(Geometry a)

Parameters

Type	Name	Description
Geometry	a	A geometry

Returns

Type	Description
PrecisionModel	A suitable precision model for overlay

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RobustScale(Geometry)

Determines a scale factor which maximizes the digits of precision and is safe to use for overlay operations. The robust scale is the minimum of the inherent scale and the safe scale factors.

Declaration

public static double RobustScale(Geometry a)

Parameters

Type	Name	Description
Geometry	a	A geometry

Returns

Type	Description
double	A scale factor for use in overlay operations

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RobustScale(Geometry, Geometry)

Determines a scale factor which maximizes the digits of precision and is safe to use for overlay operations. The robust scale is the minimum of the inherent scale and the safe scale factors.

WARNING: this is very slow.

Declaration

public static double RobustScale(Geometry a, Geometry b)

Parameters

Type	Name	Description
Geometry	a	A geometry
Geometry	b	A geometry

Returns

Type	Description
double	A scale factor for use in overlay operations

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SafeScale(Geometry)

Computes a safe scale factor for a geometry. A safe scale factor ensures that rounded number has no more than MAX_ROBUST_DP_DIGITS digits of precision.

Declaration

public static double SafeScale(Geometry geom)

Parameters

Type	Name	Description
Geometry	geom	A geometry.

Returns

Type	Description
double	A safe scale factor for the geometry ordinates

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SafeScale(Geometry, Geometry)

Computes a safe scale factor for two geometry. A safe scale factor ensures that rounded number has no more than MAX_ROBUST_DP_DIGITS digits of precision.

Declaration

public static double SafeScale(Geometry a, Geometry b)

Parameters

Type	Name	Description
Geometry	a	A geometry.
Geometry	b	A geometry (which may be `null`).

Returns

Type	Description
double	A safe scale factor for the geometry ordinates

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SafeScale(double)

Computes a safe scale factor for a numeric value. A safe scale factor ensures that rounded number has no more than MAX_ROBUST_DP_DIGITS digits of precision.

Declaration

public static double SafeScale(double value)

Parameters

Type	Name	Description
double	value	A numeric value.

Returns

Type	Description
double	A safe scale factor for the value