GEOS
3.8.0dev

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)  
Creates a PrecisionModel specifying an explicit precision model type. More...  
PrecisionModel (double newScale, double newOffsetX, double newOffsetY)  
Creates a PrecisionModel with Fixed precision. More...  
PrecisionModel (double newScale)  
Creates a PrecisionModel with Fixed precision. More...  
PrecisionModel (const PrecisionModel &pm)  
~PrecisionModel (void)  
destructor  
double  makePrecise (double val) const 
Rounds a numeric value to the PrecisionModel grid. More...  
void  makePrecise (Coordinate &coord) const 
Rounds the given Coordinate to the PrecisionModel grid.  
void  makePrecise (Coordinate *coord) const 
bool  isFloating () const 
Tests whether the precision model supports floating point. More...  
int  getMaximumSignificantDigits () const 
Returns the maximum number of significant digits provided by this precision model. More...  
Type  getType () const 
Gets the type of this PrecisionModel. More...  
double  getScale () const 
Returns the multiplying factor used to obtain a precise coordinate.  
double  getOffsetX () const 
Returns the xoffset used to obtain a precise coordinate. More...  
double  getOffsetY () const 
Returns the yoffset used to obtain a precise coordinate. More...  
std::string  toString () const 
Sets internal to the precise representation of external . More...  
int  compareTo (const PrecisionModel *other) const 
Compares this PrecisionModel object with the specified object for order. More...  
Static Public Attributes  
static const double  maximumPreciseValue 
The maximum precise value representable in a double. More...  
Friends  
class  io::Unload 
Specifies the precision model of the Coordinate in a Geometry.
In other words, specifies the grid of allowable points for all Geometry
s.
The makePrecise 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:
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 doubleprecision values. Since Java uses the IEEE394 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.
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.
scale  amount by which to multiply a coordinate after subtracting the offset, to obtain a precise coordinate 
offsetX  not used. 
offsetY  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.
newScale  amount by which to multiply a coordinate after subtracting the offset, to obtain a precise coordinate 
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 
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.
Type geos::geom::PrecisionModel::getType  (  )  const 
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.
std::string geos::geom::PrecisionModel::toString  (  )  const 
Sets internal
to the precise representation of external
.
external  the original coordinate 
internal  the coordinate whose values will be changed to the precise representation of external 

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.