QgsDistanceArea Class Reference
[Core]

#include <qgsdistancearea.h>

Collaboration diagram for QgsDistanceArea:

[legend]List of all members.

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Detailed Description

General purpose distance and area calculator.

• calculations are done on ellipsoid
• it's possible to pass points/features in any CRS, coordinates are transformed
• two options how to use it + use measure() takes QgsGeometry as a parameter and calculates distance or area + use directly measureLine(), measurePolygon() which take list of QgsPoints (both cases transform the coordinates from source CRS to the ellipse coords)
• returned values are in meters resp. square meters

Definition at line 35 of file qgsdistancearea.h.

Public Member Functions
	QgsDistanceArea ()
	Constructor.
	~QgsDistanceArea ()
	Destructor.
void	setProjectionsEnabled (bool flag)
	sets whether coordinates must be projected to ellipsoid before measuring
bool	hasCrsTransformEnabled ()
	returns projections enabled flag
void	setSourceCrs (long srsid)
	sets source spatial reference system (by QGIS CRS)
void	setSourceEpsgCrsId (long epsgId)
	sets source spatial reference system (by EpsgCrsId)
long	sourceCrs ()
	returns source spatial reference system
bool	geographic ()
	What sort of coordinate system is being used?
bool	setEllipsoid (const QString &ellipsoid)
	sets ellipsoid by its acronym
const QString &	ellipsoid ()
	returns ellipsoid's acronym
double	ellipsoidSemiMajor ()
	returns ellipsoid's semi major axis
double	ellipsoidSemiMinor ()
	returns ellipsoid's semi minor axis
double	ellipsoidInverseFlattening ()
	returns ellipsoid's inverse flattening
double	measure (QgsGeometry *geometry)
	general measurement (line distance or polygon area)
double	measureLine (const QList< QgsPoint > &points)
	measures line with more segments
double	measureLine (const QgsPoint &p1, const QgsPoint &p2)
	measures line with one segment
double	measurePolygon (const QList< QgsPoint > &points)
	measures polygon area
double	bearing (const QgsPoint &p1, const QgsPoint &p2)
	compute bearing - in radians
Static Public Member Functions
static QString	textUnit (double value, int decimals, QGis::UnitType u, bool isArea)
Protected Member Functions
unsigned char *	measureLine (unsigned char *feature, double *area)
	measures line distance, line points are extracted from WKB
unsigned char *	measurePolygon (unsigned char *feature, double *area)
	measures polygon area, vertices are extracted from WKB
double	computeDistanceBearing (const QgsPoint &p1, const QgsPoint &p2, double *course1=NULL, double *course2=NULL)
	calculates distance from two points on ellipsoid based on inverse Vincenty's formulae
double	computePolygonArea (const QList< QgsPoint > &points)
	calculates area of polygon on ellipsoid algorithm has been taken from GRASS: gis/area_poly1.c
double	computePolygonFlatArea (const QList< QgsPoint > &points)
void	computeAreaInit ()
	precalculates some values (must be called always when changing ellipsoid)
Private Member Functions
double	getQ (double x)
double	getQbar (double x)
Private Attributes
QgsCoordinateTransform *	mCoordTransform
	used for transforming coordinates from source CRS to ellipsoid's coordinates
bool	mProjectionsEnabled
	indicates whether we will transform coordinates
long	mSourceRefSys
	id of the source spatial reference system
QString	mEllipsoid
	ellipsoid acronym (from table tbl_ellipsoids)
double	mSemiMajor
	ellipsoid parameters
double	mSemiMinor
double	mInvFlattening
double	m_QA
double	m_QB
double	m_QC
double	m_QbarA
double	m_QbarB
double	m_QbarC
double	m_QbarD
double	m_AE
double	m_Qp
double	m_E
double	m_TwoPI

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Constructor & Destructor Documentation

QgsDistanceArea::QgsDistanceArea

(

)

Constructor.

Definition at line 42 of file qgsdistancearea.cpp.

References GEO_EPSG_CRS_ID, mCoordTransform, mProjectionsEnabled, setEllipsoid(), and setSourceEpsgCrsId().

QgsDistanceArea::~QgsDistanceArea

(

)

Destructor.

Definition at line 52 of file qgsdistancearea.cpp.

References mCoordTransform.

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Member Function Documentation

void QgsDistanceArea::setProjectionsEnabled

(

bool

flag

)

sets whether coordinates must be projected to ellipsoid before measuring

Definition at line 58 of file qgsdistancearea.cpp.

References mProjectionsEnabled.

Referenced by QgsMapRenderer::setProjectionsEnabled().

bool QgsDistanceArea::hasCrsTransformEnabled

(

)

[inline]

returns projections enabled flag

Definition at line 48 of file qgsdistancearea.h.

void QgsDistanceArea::setSourceCrs

(

long

srsid

)

sets source spatial reference system (by QGIS CRS)

Definition at line 63 of file qgsdistancearea.cpp.

References QgsCoordinateReferenceSystem::createFromSrsId(), mCoordTransform, and QgsCoordinateTransform::setSourceCrs().

Referenced by QgsMapRenderer::setDestinationSrs().

void QgsDistanceArea::setSourceEpsgCrsId

(

long

epsgId

)

sets source spatial reference system (by EpsgCrsId)

Definition at line 70 of file qgsdistancearea.cpp.

References QgsCoordinateReferenceSystem::createFromEpsg(), mCoordTransform, and QgsCoordinateTransform::setSourceCrs().

Referenced by QgsDistanceArea().

long QgsDistanceArea::sourceCrs

(

)

[inline]

returns source spatial reference system

Definition at line 57 of file qgsdistancearea.h.

bool QgsDistanceArea::geographic

(

)

[inline]

What sort of coordinate system is being used?

Definition at line 59 of file qgsdistancearea.h.

bool QgsDistanceArea::setEllipsoid

(

const QString &

ellipsoid

)

sets ellipsoid by its acronym

Definition at line 78 of file qgsdistancearea.cpp.

References computeAreaInit(), QgsCoordinateReferenceSystem::createFromProj4(), mCoordTransform, mEllipsoid, mInvFlattening, mSemiMajor, mSemiMinor, QgsApplication::qgisUserDbFilePath(), QgsDebugMsg, and QgsCoordinateTransform::setDestCRS().

Referenced by QgsDistanceArea().

const QString& QgsDistanceArea::ellipsoid

(

)

[inline]

returns ellipsoid's acronym

Definition at line 65 of file qgsdistancearea.h.

double QgsDistanceArea::ellipsoidSemiMajor

(

)

[inline]

returns ellipsoid's semi major axis

Definition at line 68 of file qgsdistancearea.h.

double QgsDistanceArea::ellipsoidSemiMinor

(

)

[inline]

returns ellipsoid's semi minor axis

Definition at line 70 of file qgsdistancearea.h.

double QgsDistanceArea::ellipsoidInverseFlattening

(

)

[inline]

returns ellipsoid's inverse flattening

Definition at line 72 of file qgsdistancearea.h.

double QgsDistanceArea::measure

(

QgsGeometry *

geometry

)

general measurement (line distance or polygon area)

Definition at line 177 of file qgsdistancearea.cpp.

References QgsGeometry::asWkb(), measureLine(), measurePolygon(), QgsDebugMsg, QGis::WKBLineString, QGis::WKBMultiLineString, QGis::WKBMultiPolygon, and QGis::WKBPolygon.

double QgsDistanceArea::measureLine

(

const QList< QgsPoint > &

points

)

measures line with more segments

Definition at line 249 of file qgsdistancearea.cpp.

References computeDistanceBearing(), mCoordTransform, mEllipsoid, mProjectionsEnabled, QgsCoordinateTransform::transform(), and QgsLogger::warning().

Referenced by measure(), and measureLine().

double QgsDistanceArea::measureLine	(	const QgsPoint &	p1,
		const QgsPoint &	p2
	)

measures line with one segment

Definition at line 291 of file qgsdistancearea.cpp.

References computeDistanceBearing(), mCoordTransform, mEllipsoid, mProjectionsEnabled, QgsCoordinateTransform::transform(), QgsLogger::warning(), QgsPoint::x(), and QgsPoint::y().

double QgsDistanceArea::measurePolygon

(

const QList< QgsPoint > &

points

)

measures polygon area

Definition at line 379 of file qgsdistancearea.cpp.

References computePolygonArea(), mCoordTransform, mEllipsoid, mProjectionsEnabled, QgsCoordinateTransform::transform(), and QgsLogger::warning().

Referenced by measure().

double QgsDistanceArea::bearing	(	const QgsPoint &	p1,
		const QgsPoint &	p2
	)

compute bearing - in radians

Definition at line 407 of file qgsdistancearea.cpp.

References computeDistanceBearing(), mCoordTransform, mEllipsoid, mProjectionsEnabled, and QgsCoordinateTransform::transform().

QString QgsDistanceArea::textUnit	(	double	value,
		int	decimals,
		QGis::UnitType	u,
		bool	isArea
	)			[static]

Definition at line 635 of file qgsdistancearea.cpp.

References QGis::Degrees, QGis::Feet, QGis::Meters, QgsDebugMsg, and QGis::UnknownUnit.

unsigned char * QgsDistanceArea::measureLine	(	unsigned char *	feature,
		double *	area
	)			[protected]

measures line distance, line points are extracted from WKB

Definition at line 225 of file qgsdistancearea.cpp.

References measureLine(), and QgsDebugMsg.

unsigned char * QgsDistanceArea::measurePolygon	(	unsigned char *	feature,
		double *	area
	)			[protected]

measures polygon area, vertices are extracted from WKB

Definition at line 316 of file qgsdistancearea.cpp.

References computePolygonArea(), mCoordTransform, mEllipsoid, mProjectionsEnabled, QgsCoordinateTransform::transform(), and QgsLogger::warning().

double QgsDistanceArea::computeDistanceBearing	(	const QgsPoint &	p1,
		const QgsPoint &	p2,
		double *	course1 = NULL,
		double *	course2 = NULL
	)			[protected]

calculates distance from two points on ellipsoid based on inverse Vincenty's formulae

Points p1 and p2 are expected to be in degrees and in currently used ellipsoid

Note:

if course1 is not NULL, bearing (in radians) from first point is calculated (the same for course2)

Returns:

distance in meters

Definition at line 425 of file qgsdistancearea.cpp.

References DEG2RAD, M_PI, mInvFlattening, mSemiMajor, mSemiMinor, QgsPoint::x(), and QgsPoint::y().

Referenced by bearing(), and measureLine().

double QgsDistanceArea::computePolygonArea

(

const QList< QgsPoint > &

points

)

[protected]

calculates area of polygon on ellipsoid algorithm has been taken from GRASS: gis/area_poly1.c

Definition at line 559 of file qgsdistancearea.cpp.

References computePolygonFlatArea(), DEG2RAD, getQ(), getQbar(), m_AE, m_E, M_PI, m_Qp, m_TwoPI, mEllipsoid, mProjectionsEnabled, and QgsDebugMsg.

Referenced by measurePolygon().

double QgsDistanceArea::computePolygonFlatArea

(

const QList< QgsPoint > &

points

)

[protected]

Definition at line 614 of file qgsdistancearea.cpp.

Referenced by computePolygonArea().

void QgsDistanceArea::computeAreaInit

(

)

[protected]

precalculates some values (must be called always when changing ellipsoid)

Definition at line 531 of file qgsdistancearea.cpp.

References getQ(), m_AE, m_E, M_PI, m_QA, m_QB, m_QbarA, m_QbarB, m_QbarC, m_QbarD, m_QC, m_Qp, m_TwoPI, mSemiMajor, and mSemiMinor.

Referenced by setEllipsoid().

double QgsDistanceArea::getQ

(

double

x

)

[private]

Definition at line 509 of file qgsdistancearea.cpp.

References m_QA, m_QB, and m_QC.

Referenced by computeAreaInit(), and computePolygonArea().

double QgsDistanceArea::getQbar

(

double

x

)

[private]

Definition at line 520 of file qgsdistancearea.cpp.

References m_QbarA, m_QbarB, m_QbarC, and m_QbarD.

Referenced by computePolygonArea().

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Member Data Documentation

QgsCoordinateTransform* QgsDistanceArea::mCoordTransform [private]

used for transforming coordinates from source CRS to ellipsoid's coordinates

Definition at line 129 of file qgsdistancearea.h.

Referenced by bearing(), measureLine(), measurePolygon(), QgsDistanceArea(), setEllipsoid(), setSourceCrs(), setSourceEpsgCrsId(), and ~QgsDistanceArea().

bool QgsDistanceArea::mProjectionsEnabled [private]

indicates whether we will transform coordinates

Definition at line 132 of file qgsdistancearea.h.

Referenced by bearing(), computePolygonArea(), measureLine(), measurePolygon(), QgsDistanceArea(), and setProjectionsEnabled().

long QgsDistanceArea::mSourceRefSys [private]

id of the source spatial reference system

Definition at line 135 of file qgsdistancearea.h.

QString QgsDistanceArea::mEllipsoid [private]

ellipsoid acronym (from table tbl_ellipsoids)

Definition at line 138 of file qgsdistancearea.h.

Referenced by bearing(), computePolygonArea(), measureLine(), measurePolygon(), and setEllipsoid().

double QgsDistanceArea::mSemiMajor [private]

ellipsoid parameters

Definition at line 141 of file qgsdistancearea.h.

Referenced by computeAreaInit(), computeDistanceBearing(), and setEllipsoid().

double QgsDistanceArea::mSemiMinor [private]

Definition at line 141 of file qgsdistancearea.h.

Referenced by computeAreaInit(), computeDistanceBearing(), and setEllipsoid().

double QgsDistanceArea::mInvFlattening [private]

Definition at line 141 of file qgsdistancearea.h.

Referenced by computeDistanceBearing(), and setEllipsoid().

double QgsDistanceArea::m_QA [private]

Definition at line 150 of file qgsdistancearea.h.

Referenced by computeAreaInit(), and getQ().

double QgsDistanceArea::m_QB [private]

Definition at line 150 of file qgsdistancearea.h.

Referenced by computeAreaInit(), and getQ().

double QgsDistanceArea::m_QC [private]

Definition at line 150 of file qgsdistancearea.h.

Referenced by computeAreaInit(), and getQ().

double QgsDistanceArea::m_QbarA [private]

Definition at line 151 of file qgsdistancearea.h.

Referenced by computeAreaInit(), and getQbar().

double QgsDistanceArea::m_QbarB [private]

Definition at line 151 of file qgsdistancearea.h.

Referenced by computeAreaInit(), and getQbar().

double QgsDistanceArea::m_QbarC [private]

Definition at line 151 of file qgsdistancearea.h.

Referenced by computeAreaInit(), and getQbar().

double QgsDistanceArea::m_QbarD [private]

Definition at line 151 of file qgsdistancearea.h.

Referenced by computeAreaInit(), and getQbar().

double QgsDistanceArea::m_AE [private]

Definition at line 152 of file qgsdistancearea.h.

Referenced by computeAreaInit(), and computePolygonArea().

double QgsDistanceArea::m_Qp [private]

Definition at line 153 of file qgsdistancearea.h.

Referenced by computeAreaInit(), and computePolygonArea().

double QgsDistanceArea::m_E [private]

Definition at line 154 of file qgsdistancearea.h.

Referenced by computeAreaInit(), and computePolygonArea().

double QgsDistanceArea::m_TwoPI [private]

Definition at line 155 of file qgsdistancearea.h.

Referenced by computeAreaInit(), and computePolygonArea().

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The documentation for this class was generated from the following files:

• src/core/qgsdistancearea.h
• src/core/qgsdistancearea.cpp

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