GEOS
3.14.0dev

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.  
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 (CoordinateXY &coord) const 
Rounds the given Coordinate to the PrecisionModel grid.  
void  makePrecise (CoordinateXY *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.  
double  getGridSize () const 
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 
Friends  
class  io::Unload 
Specifies the precision model of the Coordinate in a Geometry.
In other words, specifies the grid of allowable points for a Geometry
. A precision model may be floating (PrecisionModel::Type::FLOATING or PrecisionModel::Type::FLOATING_SINGLE), in which case normal floatingpoint value semantics apply.
For a PrecisionModel::Type::FIXED precision model the makePrecise(geom::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 boolean operations) always round computed coordinates to the appropriate precision model.
Three types of precision model are supported:
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. For example, to specify rounding to the nearest 1000 use a scale factor of 1000.
Coordinates are represented internally as Java doubleprecision values. Java uses the IEEE394 floating point standard, which provides 53 bits of precision. (Thus the maximum precisely representable integer is 9,007,199,254,740,992).
The types of Precision Model which GEOS supports.
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.
nModelType  the type of the precision model 
geos::geom::PrecisionModel::PrecisionModel  (  double  newScale, 
double  newOffsetX,  
double  newOffsetY  
) 
Creates a PrecisionModel
with Fixed precision.
Fixedprecision coordinates are represented as precise internal coordinates, which are rounded to the grid defined by the scale factor.
newScale  amount by which to multiply a coordinate after subtracting the offset, to obtain a precise coordinate 
newOffsetX  not used. 
newOffsetY  not used. 
geos::geom::PrecisionModel::PrecisionModel  (  double  newScale  ) 
Creates a PrecisionModel with Fixed precision.
Fixedprecision 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.
newScale  amount by which to multiply a coordinate after subtracting the offset, to obtain a precise coordinate. Must be nonzero. 
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.
other  the PrecisionModel with which this PrecisionModel is being compared 

inline 
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 explicitly (via a negative scale factor) it will be returned.
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.
double geos::geom::PrecisionModel::getOffsetX  (  )  const 
Returns the xoffset used to obtain a precise coordinate.
double geos::geom::PrecisionModel::getOffsetY  (  )  const 
Returns the yoffset used to obtain a precise coordinate.

inline 
Gets the type of this PrecisionModel
bool geos::geom::PrecisionModel::isFloating  (  )  const 
Tests whether the precision model supports floating point
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.

static 
The maximum precise value representable in a double.
Since IEE754 doubleprecision numbers allow 53 bits of mantissa, the value is equal to 2^53  1. This provides almost 16 decimal digits of precision.