Find a sequence of points on a single rhumb line. More...

#include <Rhumb.hpp>

Public Types
enum	mask { NONE, LATITUDE, LONGITUDE, AZIMUTH, DISTANCE, AREA, LONG_UNROLL, ALL }

Public Member Functions
void	GenPosition (real s12, unsigned outmask, real &lat2, real &lon2, real &S12) const

void	Position (real s12, real &lat2, real &lon2) const

void	Position (real s12, real &lat2, real &lon2, real &S12) const

Inspector functions
Math::real	Latitude () const

Math::real	Longitude () const

Math::real	Azimuth () const

Math::real	MajorRadius () const

Math::real	Flattening () const

Private Types
typedef Math::real	real

Private Member Functions
RhumbLine &	operator= (const RhumbLine &)

	RhumbLine (const Rhumb &rh, real lat1, real lon1, real azi12, bool exact)

Private Attributes
real	_azi12

real	_calp

bool	_exact

real	_lat1

real	_lon1

real	_mu1

real	_psi1

real	_r1

const Rhumb &	_rh

real	_salp

Friends
class	Rhumb

Detailed Description

Find a sequence of points on a single rhumb line.

RhumbLine facilitates the determination of a series of points on a single rhumb line. The starting point (lat1, lon1) and the azimuth azi12 are specified in the call to Rhumb::Line which returns a RhumbLine object. RhumbLine.Position returns the location of point 2 (and, optionally, the corresponding area, S12) a distance s12 along the rhumb line.

There is no public constructor for this class. (Use Rhumb::Line to create an instance.) The Rhumb object used to create a RhumbLine must stay in scope as long as the RhumbLine.

Example of use:

// Example of using the GeographicLib::RhumbLine class
 
#include <iostream>
#include <iomanip>
#include <exception>
#include <cmath>
#include <GeographicLib/Rhumb.hpp>
#include <GeographicLib/Constants.hpp>
 
using namespace std;
using namespace GeographicLib;
 
int main() {
  try {
    // Print waypoints between JFK and SIN
    Rhumb rhumb(Constants::WGS84_a(), Constants::WGS84_f());
    // Alternatively: const Rhumb& rhumb = Rhumb::WGS84();
    double
      lat1 = 40.640, lon1 = -73.779, // JFK
      lat2 =  1.359, lon2 = 103.989; // SIN
    double s12, azi12;
    rhumb.Inverse(lat1, lon1, lat2, lon2, s12, azi12);
    const GeographicLib::RhumbLine line = rhumb.Line(lat1, lon1, azi12);
    // Alternatively
    // const GeographicLib::RhumbLine line = rhumb.Line(lat1, lon1, azi1);
    double ds0 = 500e3;             // Nominal distance between points = 500 km
    int num = int(ceil(s12 / ds0)); // The number of intervals
    cout << fixed << setprecision(3);
    {
      // Use intervals of equal length
      double ds = s12 / num;
      for (int i = 0; i <= num; ++i) {
        double lat, lon;
       line.Position(i * ds, lat, lon);
       cout << i << " " << lat << " " << lon << "\n";
      }
    }
  }
  catch (const exception& e) {
    cerr << "Caught exception: " << e.what() << "\n";
    return 1;
  }
}

Definition at line 437 of file Rhumb.hpp.

Member Typedef Documentation

◆ real

typedef Math::real GeographicLib::RhumbLine::real

private

Definition at line 439 of file Rhumb.hpp.

Member Enumeration Documentation

◆ mask

enum GeographicLib::RhumbLine::mask

This is a duplication of Rhumb::mask.

Enumerator
NONE	No output.
LATITUDE	Calculate latitude lat2.
LONGITUDE	Calculate longitude lon2.
AZIMUTH	Calculate azimuth azi12.
DISTANCE	Calculate distance s12.
AREA	Calculate area S12.
LONG_UNROLL	Unroll lon2 in the direct calculation.
ALL	Calculate everything. (LONG_UNROLL is not included in this mask.)

Definition at line 452 of file Rhumb.hpp.

Constructor & Destructor Documentation

◆ RhumbLine()

GeographicLib::RhumbLine::RhumbLine	(	const Rhumb &	rh,
		real	lat1,
		real	lon1,
		real	azi12,
		bool	exact
	)

private

Definition at line 331 of file src/Rhumb.cpp.

Member Function Documentation

◆ Azimuth()

Math::real GeographicLib::RhumbLine::Azimuth ( ) const

inline

Returns: azi12 the azimuth of the rhumb line (degrees).

Definition at line 573 of file Rhumb.hpp.

◆ Flattening()

Math::real GeographicLib::RhumbLine::Flattening ( ) const

inline

Returns: f the flattening of the ellipsoid. This is the value inherited from the Rhumb object used in the constructor.

Definition at line 585 of file Rhumb.hpp.

◆ GenPosition()

void GeographicLib::RhumbLine::GenPosition	(	real	s12,
		unsigned	outmask,
		real &	lat2,
		real &	lon2,
		real &	S12
	)		const

The general position routine. RhumbLine::Position is defined in term so this function.

Parameters

[in]	s12	distance between point 1 and point 2 (meters); it can be negative.
[in]	outmask	a bitor'ed combination of RhumbLine::mask values specifying which of the following parameters should be set.
[out]	lat2	latitude of point 2 (degrees).
[out]	lon2	longitude of point 2 (degrees).
[out]	S12	area under the rhumb line (meters²).

The RhumbLine::mask values possible for outmask are

outmask |= RhumbLine::LATITUDE for the latitude lat2;
outmask |= RhumbLine::LONGITUDE for the latitude lon2;
outmask |= RhumbLine::AREA for the area S12;
outmask |= RhumbLine::ALL for all of the above;
outmask |= RhumbLine::LONG_UNROLL to unroll lon2 instead of wrapping it into the range [−180°, 180°].

With the RhumbLine::LONG_UNROLL bit set, the quantity lon2 − lon1 indicates how many times and in what sense the rhumb line encircles the ellipsoid.

If s12 is large enough that the rhumb line crosses a pole, the longitude of point 2 is indeterminate (a NaN is returned for lon2 and S12).

Definition at line 347 of file src/Rhumb.cpp.

◆ Latitude()

Math::real GeographicLib::RhumbLine::Latitude ( ) const

inline

Returns: lat1 the latitude of point 1 (degrees).

Definition at line 563 of file Rhumb.hpp.

◆ Longitude()

Math::real GeographicLib::RhumbLine::Longitude ( ) const

inline

Returns: lon1 the longitude of point 1 (degrees).

Definition at line 568 of file Rhumb.hpp.

◆ MajorRadius()

Math::real GeographicLib::RhumbLine::MajorRadius ( ) const

inline

Returns: a the equatorial radius of the ellipsoid (meters). This is the value inherited from the Rhumb object used in the constructor.

Definition at line 579 of file Rhumb.hpp.

◆ operator=()

RhumbLine& GeographicLib::RhumbLine::operator= ( const RhumbLine & )

private

◆ Position() [1/2]

void GeographicLib::RhumbLine::Position	(	real	s12,
		real &	lat2,
		real &	lon2
	)		const

inline

Compute the position of point 2 which is a distance s12 (meters) from point 1. The area is not computed.

Definition at line 520 of file Rhumb.hpp.

◆ Position() [2/2]

void GeographicLib::RhumbLine::Position	(	real	s12,
		real &	lat2,
		real &	lon2,
		real &	S12
	)		const

inline

Compute the position of point 2 which is a distance s12 (meters) from point 1. The area is also computed.

Parameters

[in]	s12	distance between point 1 and point 2 (meters); it can be negative.
[out]	lat2	latitude of point 2 (degrees).
[out]	lon2	longitude of point 2 (degrees).
[out]	S12	area under the rhumb line (meters²).

The value of lon2 returned is in the range [−180°, 180°].

If s12 is large enough that the rhumb line crosses a pole, the longitude of point 2 is indeterminate (a NaN is returned for lon2 and S12).

Definition at line 512 of file Rhumb.hpp.

Friends And Related Function Documentation

◆ Rhumb

friend class Rhumb

friend

Definition at line 440 of file Rhumb.hpp.

Member Data Documentation

◆ _azi12

real GeographicLib::RhumbLine::_azi12

private

Definition at line 443 of file Rhumb.hpp.

◆ _calp

real GeographicLib::RhumbLine::_calp

private

Definition at line 443 of file Rhumb.hpp.

◆ _exact

bool GeographicLib::RhumbLine::_exact

private

Definition at line 442 of file Rhumb.hpp.

◆ _lat1

real GeographicLib::RhumbLine::_lat1

private

Definition at line 443 of file Rhumb.hpp.

◆ _lon1

real GeographicLib::RhumbLine::_lon1

private

Definition at line 443 of file Rhumb.hpp.

◆ _mu1

real GeographicLib::RhumbLine::_mu1

private

Definition at line 443 of file Rhumb.hpp.

◆ _psi1

real GeographicLib::RhumbLine::_psi1

private

Definition at line 443 of file Rhumb.hpp.

◆ _r1

real GeographicLib::RhumbLine::_r1

private

Definition at line 443 of file Rhumb.hpp.

◆ _rh

const Rhumb& GeographicLib::RhumbLine::_rh

private

Definition at line 441 of file Rhumb.hpp.

◆ _salp

real GeographicLib::RhumbLine::_salp

private

Definition at line 443 of file Rhumb.hpp.

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

Public Types

Public Member Functions

Private Types

Private Member Functions

Private Attributes

Friends

Detailed Description

Member Typedef Documentation

◆ real

Member Enumeration Documentation

◆ mask

Constructor & Destructor Documentation

◆ RhumbLine()

Member Function Documentation

◆ Azimuth()

◆ Flattening()

◆ GenPosition()

◆ Latitude()

◆ Longitude()

◆ MajorRadius()

◆ operator=()

◆ Position() [1/2]

◆ Position() [2/2]

Friends And Related Function Documentation

◆ Rhumb

Member Data Documentation

◆ _azi12

◆ _calp

◆ _exact

◆ _lat1

◆ _lon1

◆ _mu1

◆ _psi1

◆ _r1

◆ _rh

◆ _salp