GeographicLib::RhumbLine Class Reference

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

#include <GeographicLib/Rhumb.hpp>

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

Public Member Functions
	RhumbLine (const RhumbLine &)=default
void	Position (real s12, real &lat2, real &lon2, real &S12) const
void	Position (real s12, real &lat2, real &lon2) const
void	GenPosition (real s12, unsigned outmask, real &lat2, real &lon2, real &S12) const
Inspector functions
Math::real	Latitude () const
Math::real	Longitude () const
Math::real	Azimuth () const
Math::real	EquatorialRadius () const
Math::real	Flattening () const

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);
    RhumbLine line = rhumb.Line(lat1, lon1, azi12);
    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 458 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 475 of file Rhumb.hpp.

Constructor & Destructor Documentation

RhumbLine()

GeographicLib::RhumbLine::RhumbLine ( const RhumbLine &  )

default

Construction is via default copy constructor.

Member Function Documentation

Position() [1/2]

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 535 of file Rhumb.hpp.

Referenced by main().

Position() [2/2]

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 543 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 350 of file Rhumb.cpp.

References GeographicLib::Math::AngNormalize(), AREA, GeographicLib::Math::degree(), GeographicLib::Math::hd, GeographicLib::Ellipsoid::InverseRectifyingLatitude(), LATITUDE, LONG_UNROLL, LONGITUDE, GeographicLib::Math::NaN(), GeographicLib::Math::qd, and GeographicLib::Ellipsoid::QuarterMeridian().

Referenced by GeographicLib::Rhumb::GenDirect().

Latitude()

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

inline

Returns

lat1 the latitude of point 1 (degrees).

Definition at line 586 of file Rhumb.hpp.

Longitude()

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

inline

Returns

lon1 the longitude of point 1 (degrees).

Definition at line 591 of file Rhumb.hpp.

Azimuth()

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

inline

Returns

azi12 the azimuth of the rhumb line (degrees).

Definition at line 596 of file Rhumb.hpp.

EquatorialRadius()

Math::real GeographicLib::RhumbLine::EquatorialRadius ( ) 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 602 of file Rhumb.hpp.

References GeographicLib::Rhumb::EquatorialRadius().

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 608 of file Rhumb.hpp.

References GeographicLib::Rhumb::Flattening().

Friends And Related Function Documentation

Rhumb

friend class Rhumb

friend

Definition at line 461 of file Rhumb.hpp.

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

• Rhumb.hpp
• Rhumb.cpp