qgsdistancearea.h

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/***************************************************************************
  qgsdistancearea.h - Distance and area calculations on the ellipsoid
 ---------------------------------------------------------------------------
  Date                 : September 2005
  Copyright            : (C) 2005 by Martin Dobias
  email                : won.der at centrum.sk
 ***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

#ifndef QGSDISTANCEAREA_H
#define QGSDISTANCEAREA_H

#include <QList>
#include "qgscoordinatetransform.h"

class QgsGeometry;

class CORE_EXPORT QgsDistanceArea
{
  public:
    QgsDistanceArea();

    ~QgsDistanceArea();

    QgsDistanceArea( const QgsDistanceArea &origDA );

    QgsDistanceArea & operator=( const QgsDistanceArea & origDA );

    void setEllipsoidalMode( bool flag );

    bool ellipsoidalEnabled() const { return mEllipsoidalMode; }

    void setSourceCrs( long srsid );

    void setSourceCrs( const QgsCoordinateReferenceSystem& srcCRS );

    void setSourceAuthId( QString authid );

    long sourceCrs() const { return mSourceRefSys; }
    bool geographic() const { return mCoordTransform->sourceCrs().geographicFlag(); }

    bool setEllipsoid( const QString& ellipsoid );

    // Inverse flattening is calculated with invf = a/(a-b)
    bool setEllipsoid( double semiMajor, double semiMinor );

    const QString& ellipsoid() const { return mEllipsoid; }

    double ellipsoidSemiMajor() const { return mSemiMajor; }
    double ellipsoidSemiMinor() const { return mSemiMinor; }
    double ellipsoidInverseFlattening() const { return mInvFlattening; }

    double measure( QgsGeometry* geometry );

    double measurePerimeter( QgsGeometry* geometry );

    double measureLine( const QList<QgsPoint>& points );

    double measureLine( const QgsPoint& p1, const QgsPoint& p2 );

    double measurePolygon( const QList<QgsPoint>& points );

    double bearing( const QgsPoint& p1, const QgsPoint& p2 );

    static QString textUnit( double value, int decimals, QGis::UnitType u, bool isArea, bool keepBaseUnit = false );

    void convertMeasurement( double &measure, QGis::UnitType &measureUnits, QGis::UnitType displayUnits, bool isArea );

  protected:
    const unsigned char* measureLine( const unsigned char* feature, double* area, bool hasZptr = false );
    const unsigned char* measurePolygon( const unsigned char* feature, double* area, double* perimeter, bool hasZptr = false );

    double computeDistanceBearing( const QgsPoint& p1, const QgsPoint& p2,
                                   double* course1 = NULL, double* course2 = NULL );


    double computePolygonArea( const QList<QgsPoint>& points );

    double computePolygonFlatArea( const QList<QgsPoint>& points );

    void computeAreaInit();

  private:
    void _copy( const QgsDistanceArea & origDA );

    QgsCoordinateTransform* mCoordTransform;

    bool mEllipsoidalMode;

    long mSourceRefSys;

    QString mEllipsoid;

    double mSemiMajor, mSemiMinor, mInvFlattening;

    // utility functions for polygon area measurement

    double getQ( double x );
    double getQbar( double x );

    // temporary area measurement stuff

    double m_QA, m_QB, m_QC;
    double m_QbarA, m_QbarB, m_QbarC, m_QbarD;
    double m_AE;  /* a^2(1-e^2) */
    double m_Qp;  /* Q at the north pole */
    double m_E;   /* area of the earth */
    double m_TwoPI;

};

#endif