EarthField class model calculations. More...

#include <EarthField.h>

Public Types
enum	EarthFieldTypes { IGRF, NONE, STANDARD }
	Known EarthField calculation models. More...

Public Member Functions
	EarthField ()
	Default constructor, generates default J2000 EarthField identification. More...

	EarthField (const EarthField &other)
	Copy constructor. More...

	EarthField (EarthFieldTypes model, Double catepoch=51544.5)
	Constructor with epoch in MJulian days (default is J2000) More...

EarthField &	operator= (const EarthField &other)
	Copy assignment. More...

	~EarthField ()

const Vector< Double > &	operator() (const MVPosition &pos)
	Return the EarthField components. More...

const Vector< Double > *	derivative (const MVPosition &pos)
	Return derivatives of field (to X, Y, Z). More...

void	init ()
	Re-initialise EarthField object with specified model and epoch, or defaults STANDARD and J2000. More...

void	init (EarthFieldTypes model, Double catepoch=51544.5)

void	refresh ()
	Refresh calculations. More...

Static Public Attributes
static const Double	INTV
	Default interval to be used for linear approximation (in m) More...

Private Member Functions
void	copy (const EarthField &other)
	Make a copy. More...

void	fillField ()
	Create correct default fixedEpoch and catalogue field data. More...

void	calcField (const MVPosition &pos)
	Calculate EarthField for longitude and latitude and altitude (m) More...

Private Attributes
EarthFieldTypes	method_p
	Method to be used. More...

Double	fixedEpoch_p
	Fixed epoch to be used (MJD) More...

Vector< Double >	agh_p
	List of spherical components. More...

Vector< Double >	p_p
	Work arrays for calculations. More...

Vector< Double >	q_p

Vector< Double >	cl_p

Vector< Double >	sl_p

MVPosition	checkPos_p
	Check position. More...

Double	pval_p [3]
	Cached calculated field components. More...

Double	dval_p [3][3]
	Cached derivatives. More...

Int	lres_p
	To reference results, and use a few in interim calculations, results are calculated in a circular buffer. More...

Vector< Double >	result_p [4]
	Last calculation. More...

Static Private Attributes
static uInt	interval_reg_p
	Interpolation interval. More...

Detailed Description

EarthField class model calculations.

Intended use:

Internal

Review Status

Reviewed By:: UNKNOWN
Date Reviewed:: before2004/08/25
Test programs:: tEarthField

Prerequisite

Measure class for use
MeasTable class for data

Etymology

Earth magnetic Field model

Synopsis

EarthField forms the class for Earth magnetic field calculations. It is a simple container with the selected model, and the mean epoch.
The method is selected from one of the following:

EarthField::STANDARD (at 1998/05/18 the IGRF definition)
EarthField::IGRF (IGRF reference field model)

Epochs can be specified as the MJD (with defined constants MeasData::MJD2000 and MeasData::MJD1950 or the actual MJD), leading to the following constructors:

EarthField() default; assuming IGRF and MJD2000
EarthField(method); assuming J2000 as epoch
EarthField(method, epoch) with epoch Double(MJD)

Actual EarthField for a certain position on Earth is calculated by the () operator. Arguments can be:

MVPosition: a position on Earth (in the ITRF frame)

The returned value is a 3D vector of the field (in nT) in ITRF coordinates. The derivative (d^-1) can be obtained as well by derivative(MVPosition).
An EarthField can be re-initialised with a different method and/or other epoch with the init() functions (same format as constructors).

To bypass the full, lengthy calculation actual returned values are calculated using the derivative if within about 50 km (error less than about 10^-2 G). A call to refresh() will re-initiate calculations from scratch.
The following details can be set with the Aipsrc mechanism:

measures.earthfield.d_interval: approximation radius (km is default unit) over which a linear approximation is used

The field model is assumed to be constant over the time-span the class is used.

The calculations are based on a routine provided by the IGRF community. See ftp.ngdc.noaa.gov/Solid_Earth/Mainfld_Mag/Models/IAGA, routine IGRFLIB.FOR. The values are in nT (10uG).

Example

EarthField mine(EarthField::STANDARD,
45837.0);              // define EarthField type
// for 84/05/17
MPosition pos;
MeasTable::Observatory(pos, "WSRT");   // Obervatory position
// Make sure correct position frame used
MVPosition x(MPosition::Convert(pos, MPosition::ITRF)().getValue());
MVEarthMagnetic now = mine(x);         // get EarthField

Motivation

To have a container (with history) for field calculations

To Do

nothing I know off

Definition at line 130 of file EarthField.h.

Member Enumeration Documentation

enum casacore::EarthField::EarthFieldTypes

Known EarthField calculation models.

Enumerator
IGRF	Standard IGRF model.
NONE	Make the field equal to zero.
STANDARD	Standard default model if none specified.

Definition at line 140 of file EarthField.h.

Constructor & Destructor Documentation

casacore::EarthField::EarthField ( )

Default constructor, generates default J2000 EarthField identification.

casacore::EarthField::EarthField ( const EarthField & other )

Copy constructor.

casacore::EarthField::EarthField	(	EarthFieldTypes	model,
		Double	catepoch = `51544.5`
	)

explicit

Constructor with epoch in MJulian days (default is J2000)

casacore::EarthField::~EarthField ( )

Member Function Documentation

void casacore::EarthField::calcField ( const MVPosition & pos )

private

Calculate EarthField for longitude and latitude and altitude (m)

void casacore::EarthField::copy ( const EarthField & other )

private

Make a copy.

const Vector<Double>* casacore::EarthField::derivative ( const MVPosition & pos )

Return derivatives of field (to X, Y, Z).

Note that the value returned has only a lifetime as long as the EarthField container exists, and no new components or derivative is calculated. The returned value should not be deleted.

void casacore::EarthField::fillField ( )

private

Create correct default fixedEpoch and catalogue field data.

void casacore::EarthField::init ( )

Re-initialise EarthField object with specified model and epoch, or defaults STANDARD and J2000.

void casacore::EarthField::init	(	EarthFieldTypes	model,
		Double	catepoch = `51544.5`
	)

const Vector<Double>& casacore::EarthField::operator() ( const MVPosition & pos )

Return the EarthField components.

Note that the value returned has only a lifetime as long as the EarthField container exists, and no new derivative is asked for.

EarthField& casacore::EarthField::operator= ( const EarthField & other )

Copy assignment.

void casacore::EarthField::refresh ( )

Refresh calculations.

Member Data Documentation

Vector<Double> casacore::EarthField::agh_p

private

List of spherical components.

Definition at line 190 of file EarthField.h.

MVPosition casacore::EarthField::checkPos_p

private

Check position.

Definition at line 199 of file EarthField.h.

Vector<Double> casacore::EarthField::cl_p

private

Definition at line 195 of file EarthField.h.

Double casacore::EarthField::dval_p[3][3]

private

Cached derivatives.

Definition at line 203 of file EarthField.h.

Double casacore::EarthField::fixedEpoch_p

private

Fixed epoch to be used (MJD)

Definition at line 188 of file EarthField.h.

uInt casacore::EarthField::interval_reg_p

staticprivate

Interpolation interval.

Definition at line 211 of file EarthField.h.

const Double casacore::EarthField::INTV

static

Default interval to be used for linear approximation (in m)

Definition at line 136 of file EarthField.h.

Int casacore::EarthField::lres_p

private

To reference results, and use a few in interim calculations, results are calculated in a circular buffer.

Current result pointer

Definition at line 207 of file EarthField.h.

EarthFieldTypes casacore::EarthField::method_p

private

Method to be used.

Definition at line 186 of file EarthField.h.

Vector<Double> casacore::EarthField::p_p

private

Work arrays for calculations.

Definition at line 193 of file EarthField.h.

Double casacore::EarthField::pval_p[3]

private

Cached calculated field components.

Definition at line 201 of file EarthField.h.

Vector<Double> casacore::EarthField::q_p

private

Definition at line 194 of file EarthField.h.

Vector<Double> casacore::EarthField::result_p[4]

private

Last calculation.

Definition at line 209 of file EarthField.h.

Vector<Double> casacore::EarthField::sl_p

private

Definition at line 196 of file EarthField.h.

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

casa/casacore/measures/Measures/EarthField.h

Public Types

Public Member Functions

Static Public Attributes

Private Member Functions

Private Attributes

Static Private Attributes

Detailed Description

Intended use:

Review Status

Prerequisite

Etymology

Synopsis

Example

Motivation

To Do

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation