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

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

private

Definition at line 39 of file MagneticCircle.hpp.

Constructor & Destructor Documentation

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.

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.

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

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.

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.

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

inline

Returns: the height of the circle (meters).

Definition at line 167 of file MagneticCircle.hpp.

bool GeographicLib::MagneticCircle::Init ( ) const

inline

Returns: true if the object has been initialized.

Definition at line 145 of file MagneticCircle.hpp.

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

inline

Returns: the latitude of the circle (degrees).

Definition at line 162 of file MagneticCircle.hpp.

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.

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.

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.

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

friend class MagneticModel

friend

Definition at line 89 of file MagneticCircle.hpp.

Member Data Documentation

real GeographicLib::MagneticCircle::_a

private

Definition at line 41 of file MagneticCircle.hpp.

CircularEngine GeographicLib::MagneticCircle::_circ0

private

Definition at line 43 of file MagneticCircle.hpp.

CircularEngine GeographicLib::MagneticCircle::_circ1

private

Definition at line 43 of file MagneticCircle.hpp.

CircularEngine GeographicLib::MagneticCircle::_circ2

private

Definition at line 43 of file MagneticCircle.hpp.

bool GeographicLib::MagneticCircle::_constterm

private

Definition at line 42 of file MagneticCircle.hpp.

real GeographicLib::MagneticCircle::_cphi

private

Definition at line 41 of file MagneticCircle.hpp.

real GeographicLib::MagneticCircle::_dt0

private

Definition at line 41 of file MagneticCircle.hpp.

real GeographicLib::MagneticCircle::_f

private

Definition at line 41 of file MagneticCircle.hpp.

real GeographicLib::MagneticCircle::_h

private

Definition at line 41 of file MagneticCircle.hpp.

bool GeographicLib::MagneticCircle::_interpolate

private

Definition at line 42 of file MagneticCircle.hpp.

real GeographicLib::MagneticCircle::_lat

private

Definition at line 41 of file MagneticCircle.hpp.

real GeographicLib::MagneticCircle::_sphi

private

Definition at line 41 of file MagneticCircle.hpp.

real GeographicLib::MagneticCircle::_t

private

Definition at line 41 of file MagneticCircle.hpp.

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

Constructor & Destructor Documentation

Member Function Documentation

Friends And Related Function Documentation

Member Data Documentation