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## com.vividsolutions.jts.geom
Class PrecisionModel

    java.lang.Object
      com.vividsolutions.jts.geom.PrecisionModel

All Implemented Interfaces:
  java.io.Serializable, java.lang.Comparable

    public class PrecisionModel

extends java.lang.Object
implements java.io.Serializable, java.lang.Comparable

Specifies the precision model of the `Coordinate`s in a `Geometry`. In other words, specifies the grid of allowable points for all `Geometry`s.

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. 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 size of 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.

Version:
  1.7
See Also:
  Serialized Form

Nested Class Summary
`static class` | `PrecisionModel.Type` The types of Precision Model which JTS supports.

Field Summary
`static PrecisionModel.Type` | `FIXED` Fixed Precision indicates that coordinates have a fixed number of decimal places.
`static PrecisionModel.Type` | `FLOATING` Floating precision corresponds to the standard Java double-precision floating-point representation, which is based on the IEEE-754 standard
`static 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(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 scale factor used to specify a fixed precision model.
`PrecisionModel.Type` | `getType()` Gets the type of this precision model
`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 `PrecisionModel`s 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 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 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 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(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 `PrecisionModel`s 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 decimal representations of precise values (such as `WKTWriter`).

  This method would be more correctly called `getMinimumDecimalPlaces`, since it actually computes the number of decimal places that is required to correctly display the full precision of an ordinate value.

  Since it is difficult to compute the required number of decimal places for scale factors which are not powers of 10, the algorithm uses a very rough approximation in this case. This has the side effect that for scale factors which are powers of 10 the value returned is 1 greater than the true value.

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

### getScale

    public double getScale()

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

  Returns:
    the scale factor for the fixed precision model

### getType

    public PrecisionModel.Type getType()

  Gets the type of this precision model

  Returns:
    the type of this precision model
  See Also:
    `PrecisionModel.Type`

### 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.

  This method has no effect on NaN values.

  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()

  Overrides:
    `toString` in class `java.lang.Object`

### equals

    public boolean equals(java.lang.Object other)

  Overrides:
    `equals` in class `java.lang.Object`

### 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 `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`

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