#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. | |
PrecisionModel (double newScale, double newOffsetX, double newOffsetY) | |
Creates a PrecisionModel with Fixed precision. | |
PrecisionModel (double newScale) | |
Creates a PrecisionModel with Fixed precision. | |
PrecisionModel (const PrecisionModel &pm) | |
~PrecisionModel (void) | |
destructor | |
double | makePrecise (double val) const |
Rounds a numeric value to the PrecisionModel grid. | |
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. | |
int | getMaximumSignificantDigits () const |
Returns the maximum number of significant digits provided by this precision model. | |
Type | getType () const |
Gets the type of this PrecisionModel. | |
double | getScale () const |
Returns the multiplying factor used to obtain a precise coordinate. | |
double | getOffsetX () const |
Returns the x-offset used to obtain a precise coordinate. | |
double | getOffsetY () const |
Returns the y-offset used to obtain a precise coordinate. | |
std::string | toString () const |
Sets internal to the precise representation of external . | |
int | compareTo (const PrecisionModel *other) const |
Compares this PrecisionModel object with the specified object for order. | |
Static Public Attributes | |
static const double | maximumPreciseValue |
The maximum precise value representable in a double. | |
Friends | |
class | io::Unload |
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:
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.
The types of Precision Model which GEOS supports.
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 | Floating precision corresponds to the standard Java double-precision floating-point representation, which is based on the IEEE-754 standard |
FLOATING_SINGLE | Floating single precision corresponds to the standard Java single-precision floating-point representation, which is based on the IEEE-754 standard |
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.
Fixed-precision 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.
Fixed-precision 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 |
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.
bool geos::geom::PrecisionModel::isFloating | ( | ) | const |
int geos::geom::PrecisionModel::getMaximumSignificantDigits | ( | ) | const |
Type geos::geom::PrecisionModel::getType | ( | ) | const |
double geos::geom::PrecisionModel::getOffsetX | ( | ) | const |
Returns the x-offset used to obtain a precise coordinate.
double geos::geom::PrecisionModel::getOffsetY | ( | ) | const |
Returns the y-offset used to obtain a precise coordinate.
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 |
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 |
const double geos::geom::PrecisionModel::maximumPreciseValue [static] |
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.