Geomagnetic field on a circle of latitude. More...

#include <MagneticCircle.hpp>

Public Member Functions
	MagneticCircle ()

Compute the magnetic field
void	operator() (real lon, real &Bx, real &By, real &Bz) const

void	operator() (real lon, real &Bx, real &By, real &Bz, real &Bxt, real &Byt, real &Bzt) const

Inspector functions
bool	Init () const

Math::real	MajorRadius () const

Math::real	Flattening () const

Math::real	Latitude () const

Math::real	Height () const

Math::real	Time () const

Private Types
typedef Math::real	real

Private Member Functions
void	Field (real lon, bool diffp, real &Bx, real &By, real &Bz, real &Bxt, real &Byt, real &Bzt) const

	MagneticCircle (real a, real f, real lat, real h, real t, real cphi, real sphi, real t1, real dt0, bool interpolate, const CircularEngine &circ0, const CircularEngine &circ1)

	MagneticCircle (real a, real f, real lat, real h, real t, real cphi, real sphi, real t1, real dt0, bool interpolate, const CircularEngine &circ0, const CircularEngine &circ1, const CircularEngine &circ2)

Private Attributes
real	_a

CircularEngine	_circ0

CircularEngine	_circ1

CircularEngine	_circ2

bool	_constterm

real	_cphi

real	_dt0

real	_f

real	_h

bool	_interpolate

real	_lat

real	_sphi

real	_t

real	_t1

Friends
class	MagneticModel

Detailed Description

Geomagnetic field on a circle of latitude.

Evaluate the earth's magnetic field on a circle of constant height and latitude. This uses a CircularEngine to pre-evaluate the inner sum of the spherical harmonic sum, allowing the values of the field at several different longitudes to be evaluated rapidly.

Use MagneticModel::Circle to create a MagneticCircle object. (The constructor for this class is private.)

Example of use:

// Example of using the GeographicLib::MagneticCircle class
#include <iostream>
#include <exception>
#include <GeographicLib/MagneticModel.hpp>
#include <GeographicLib/MagneticCircle.hpp>
using namespace std;
using namespace GeographicLib;
int main() {
  try {
    MagneticModel mag("wmm2010");
    double lat = 27.99, lon0 = 86.93, h = 8820, t = 2012; // Mt Everest
    {
      // Slow method of evaluating the values at several points on a circle of
      // latitude.
      for (int i = -5; i <= 5; ++i) {
        double lon = lon0 + i * 0.2;
        double Bx, By, Bz;
        mag(t, lat, lon, h, Bx, By, Bz);
        cout << lon << " " << Bx << " " << By << " " << Bz << "\n";
      }
    }
    {
      // Fast method of evaluating the values at several points on a circle of
      // latitude using MagneticCircle.
      MagneticCircle circ = mag.Circle(t, lat, h);
      for (int i = -5; i <= 5; ++i) {
        double lon = lon0 + i * 0.2;
        double Bx, By, Bz;
        circ(lon, Bx, By, Bz);
        cout << lon << " " << Bx << " " << By << " " << Bz << "\n";
      }
    }
  }
  catch (const exception& e) {
    cerr << "Caught exception: " << e.what() << "\n";
    return 1;
  }
}

MagneticField is a command-line utility providing access to the functionality of MagneticModel and MagneticCircle.

Definition at line 37 of file MagneticCircle.hpp.

Member Typedef Documentation

◆ real

typedef Math::real GeographicLib::MagneticCircle::real

private

Definition at line 39 of file MagneticCircle.hpp.

Constructor & Destructor Documentation

◆ MagneticCircle() [1/3]

GeographicLib::MagneticCircle::MagneticCircle	(	real	a,
		real	f,
		real	lat,
		real	h,
		real	t,
		real	cphi,
		real	sphi,
		real	t1,
		real	dt0,
		bool	interpolate,
		const CircularEngine &	circ0,
		const CircularEngine &	circ1
	)

inlineprivate

Definition at line 45 of file MagneticCircle.hpp.

◆ MagneticCircle() [2/3]

GeographicLib::MagneticCircle::MagneticCircle	(	real	a,
		real	f,
		real	lat,
		real	h,
		real	t,
		real	cphi,
		real	sphi,
		real	t1,
		real	dt0,
		bool	interpolate,
		const CircularEngine &	circ0,
		const CircularEngine &	circ1,
		const CircularEngine &	circ2
	)

inlineprivate

Definition at line 64 of file MagneticCircle.hpp.

◆ MagneticCircle() [3/3]

GeographicLib::MagneticCircle::MagneticCircle ( )

inline

A default constructor for the normal gravity. This sets up an uninitialized object which can be later replaced by the MagneticModel::Circle.

Definition at line 98 of file MagneticCircle.hpp.

Member Function Documentation

◆ Field()

void GeographicLib::MagneticCircle::Field	(	real	lon,
		bool	diffp,
		real &	Bx,
		real &	By,
		real &	Bz,
		real &	Bxt,
		real &	Byt,
		real &	Bzt
	)		const

private

Definition at line 19 of file src/MagneticCircle.cpp.

◆ Flattening()

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

inline

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

Definition at line 157 of file MagneticCircle.hpp.

◆ Height()

Math::real GeographicLib::MagneticCircle::Height ( ) const

inline

Returns: the height of the circle (meters).

Definition at line 167 of file MagneticCircle.hpp.

◆ Init()

bool GeographicLib::MagneticCircle::Init ( ) const

inline

Returns: true if the object has been initialized.

Definition at line 145 of file MagneticCircle.hpp.

◆ Latitude()

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

inline

Returns: the latitude of the circle (degrees).

Definition at line 162 of file MagneticCircle.hpp.

◆ MajorRadius()

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

inline

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

Definition at line 151 of file MagneticCircle.hpp.

◆ operator()() [1/2]

void GeographicLib::MagneticCircle::operator()	(	real	lon,
		real &	Bx,
		real &	By,
		real &	Bz
	)		const

inline

Evaluate the components of the geomagnetic field at a particular longitude.

Parameters

[in]	lon	longitude of the point (degrees).
[out]	Bx	the easterly component of the magnetic field (nanotesla).
[out]	By	the northerly component of the magnetic field (nanotesla).
[out]	Bz	the vertical (up) component of the magnetic field (nanotesla).

Definition at line 114 of file MagneticCircle.hpp.

◆ operator()() [2/2]

void GeographicLib::MagneticCircle::operator()	(	real	lon,
		real &	Bx,
		real &	By,
		real &	Bz,
		real &	Bxt,
		real &	Byt,
		real &	Bzt
	)		const

inline

Evaluate the components of the geomagnetic field and their time derivatives at a particular longitude.

Parameters

[in]	lon	longitude of the point (degrees).
[out]	Bx	the easterly component of the magnetic field (nanotesla).
[out]	By	the northerly component of the magnetic field (nanotesla).
[out]	Bz	the vertical (up) component of the magnetic field (nanotesla).
[out]	Bxt	the rate of change of Bx (nT/yr).
[out]	Byt	the rate of change of By (nT/yr).
[out]	Bzt	the rate of change of Bz (nT/yr).

Definition at line 133 of file MagneticCircle.hpp.

◆ Time()

Math::real GeographicLib::MagneticCircle::Time ( ) const

inline

Returns: the time (fractional years).

Definition at line 172 of file MagneticCircle.hpp.

Friends And Related Function Documentation

◆ MagneticModel

friend class MagneticModel

friend

Definition at line 89 of file MagneticCircle.hpp.

Member Data Documentation

◆ _a

real GeographicLib::MagneticCircle::_a

private

Definition at line 41 of file MagneticCircle.hpp.

◆ _circ0

CircularEngine GeographicLib::MagneticCircle::_circ0

private

Definition at line 43 of file MagneticCircle.hpp.

◆ _circ1

CircularEngine GeographicLib::MagneticCircle::_circ1

private

Definition at line 43 of file MagneticCircle.hpp.

◆ _circ2

CircularEngine GeographicLib::MagneticCircle::_circ2

private

Definition at line 43 of file MagneticCircle.hpp.

◆ _constterm

bool GeographicLib::MagneticCircle::_constterm

private

Definition at line 42 of file MagneticCircle.hpp.

◆ _cphi

real GeographicLib::MagneticCircle::_cphi

private

Definition at line 41 of file MagneticCircle.hpp.

◆ _dt0

real GeographicLib::MagneticCircle::_dt0

private

Definition at line 41 of file MagneticCircle.hpp.

◆ _f

real GeographicLib::MagneticCircle::_f

private

Definition at line 41 of file MagneticCircle.hpp.

◆ _h

real GeographicLib::MagneticCircle::_h

private

Definition at line 41 of file MagneticCircle.hpp.

◆ _interpolate

bool GeographicLib::MagneticCircle::_interpolate

private

Definition at line 42 of file MagneticCircle.hpp.

◆ _lat

real GeographicLib::MagneticCircle::_lat

private

Definition at line 41 of file MagneticCircle.hpp.

◆ _sphi

real GeographicLib::MagneticCircle::_sphi

private

Definition at line 41 of file MagneticCircle.hpp.

◆ _t

real GeographicLib::MagneticCircle::_t

private

Definition at line 41 of file MagneticCircle.hpp.

◆ _t1

real GeographicLib::MagneticCircle::_t1

private

Definition at line 41 of file MagneticCircle.hpp.

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

Public Member Functions

Private Types

Private Member Functions

Private Attributes

Friends

Detailed Description

Member Typedef Documentation

◆ real

Constructor & Destructor Documentation

◆ MagneticCircle() [1/3]

◆ MagneticCircle() [2/3]

◆ MagneticCircle() [3/3]

Member Function Documentation

◆ Field()

◆ Flattening()

◆ Height()

◆ Init()

◆ Latitude()

◆ MajorRadius()

◆ operator()() [1/2]

◆ operator()() [2/2]

◆ Time()

Friends And Related Function Documentation

◆ MagneticModel

Member Data Documentation

◆ _a

◆ _circ0

◆ _circ1

◆ _circ2

◆ _constterm

◆ _cphi

◆ _dt0

◆ _f

◆ _h

◆ _interpolate

◆ _lat

◆ _sphi

◆ _t

◆ _t1