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, real &S12) const

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

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

private

Definition at line 439 of file Rhumb.hpp.

Member Enumeration Documentation

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

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

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

inline

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

Definition at line 573 of file Rhumb.hpp.

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.

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.

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

inline

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

Definition at line 563 of file Rhumb.hpp.

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

inline

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

Definition at line 568 of file Rhumb.hpp.

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.

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

private

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.

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.

Friends And Related Function Documentation

friend class Rhumb

friend

Definition at line 440 of file Rhumb.hpp.