casacore::Projection Class Reference

Geometric parameters needed for a sky projection to a plane. More...

#include <Projection.h>

Public Types
enum	Type { AZP, SZP, TAN, SIN, STG, ARC, ZPN, ZEA, AIR, CYP, CAR, MER, CEA, COP, COD, COE, COO, BON, PCO, SFL, PAR, AIT, MOL, CSC, QSC, TSC, HPX, N_PROJ }
	Hold all the known types of celestial projections. More...
Public Member Functions
	Projection (Projection::Type which=CAR)
	Construct a projection which needs no parameters.
	Projection (const String &ctypeLin, const String &ctypeLat, const Vector< Double > &parameters)
	Construct a projection from FITS CTYPE keywords.
	Projection (Projection::Type which, const Vector< Double > &parameters)
	Construct a projection which needs parameters.
	Projection (const Projection &other)
	Copy constructor (copy semantics).
Projection &	operator= (const Projection &other)
	Assignment (copy semantics).
	~Projection ()
	Destructor.
Projection::Type	type () const
	What is the Type of this projection?
String	name () const
	What is the type of this projection as a String (e.g.
const Vector< Double > &	parameters () const
Bool	near (const Projection &other, Double tol=1.0e-6) const
	Comparison to fractional tolerance.
Static Public Member Functions
static String	name (Projection::Type proj)
static Projection::Type	type (const String &name)
	Turn a projection type name into a Type.
static uInt	nParameters (Projection::Type proj)
	How many parameters does this projection have at most? What is the minimum number of parameters that have to be supplied? What are the parameter values?
static uInt	nMinParameters (Projection::Type proj)
static Bool	isZenithal (Projection::Type proj)
	Is this projection a 'zenithal' projection.
Private Member Functions
void	validate (const Bool verbose=False)
Projection::Type	type (String &ctypeLong, String &ctypeLat) const
Private Attributes
Projection::Type	which_p
Vector< Double >	parameters_p

Detailed Description

Geometric parameters needed for a sky projection to a plane.

Intended use:

Public interface

Review Status

Reviewed By:: Peter Barnes
Date Reviewed:: 1999/12/24
Test programs:: tProjection

Prerequisite

Knowledge of astronomical coordinate conversions in general. Probably the best documents are the papers by Mark Calabretta and Eric Greisen. The initial draft from 1996 can be found at http://www.atnf.csiro.au/~mcalabre. It is this draft that the Coordinate classes are based upon. Since then, this paper has evolved into three which can be found at the above address, and will be published in the Astronomy and Astrophysics Supplement Series (probably in 2000). The design has changed since the initial draft. When these papers are finalized, and the IAU has ratified the new standards, WCSLIB (Mark Calabretta's implementation of these conventions) will be revised for the new designs. At that time, the Coordinate classes may also be revised.

Synopsis

This class is used to hold:

The type of the projection (e.g. SIN); and
The parameters of the projection, if any. These parameters are described by Calabretta and Greisen (called PROJP) in the 1996 draft. In the recent versions, this paper has split into three, and the projection parameters have been reworked into the PV matrix. However, these have not yet been implemented in WCSLIB so we stick with the old ones for now.

Example

 Projection proj(Projection::CAR);
 cerr << proj.parameters() << endl;

This projection requires no parameters so the printed parameter vector would be of zero length.

Thrown Exceptions

AipsError

To Do

Worry about projection parameters which are unit dependent (i.e. radians vs. degrees).
LONGPOLE should probably go in here.

Definition at line 95 of file Projection.h.

Member Enumeration Documentation

enum casacore::Projection::Type

Hold all the known types of celestial projections.

Enumerator:

AZP	Zenithal/Azimuthal perspective.
SZP	Slant zenithal perspective, new.
TAN	Gnomonic.
SIN	Orthographics/synthesis.
STG	Stereographic.
ARC	zenith/azimuthal equidistant.
ZPN	zenithal/azimuthal polynomial.
ZEA	zenithal/azimuthal equal area.
AIR	Airy.
CYP	Cylindrical perspective.
CAR	Plate carree.
MER	Mercator.
CEA	Cylindrical equal area.
COP	Conic perspective.
COD	Conic equidistant.
COE	Conic equal area.
COO	Conic orthomorphic.
BON	Bonne.
PCO	Polyconic.
SFL	Sanson-Flamsteed (global sinusoidal). The old GLS projection is now SFL. The 'GLS' string will be converted to 'SFL'
PAR	Parabolic.
AIT	Hammer-Aitoff.
MOL	Mollweide.
CSC	COBE quadrilateralized spherical cube.
QSC	Quadrilateralized spherical cube.
TSC	Tangential spherical cube.
HPX	HEALPix grid.
N_PROJ	N_PROJ gives the number of supported projections - it shouldn't be used as a projection.

Definition at line 99 of file Projection.h.

Constructor & Destructor Documentation

casacore::Projection::Projection ( Projection::Type which = CAR )

Construct a projection which needs no parameters.

SIN is unique in that it can be created with 0 or 2 parameters.

casacore::Projection::Projection	(	const String &	ctypeLin,
		const String &	ctypeLat,
		const Vector< Double > &	parameters
	)

Construct a projection from FITS CTYPE keywords.

casacore::Projection::Projection	(	Projection::Type	which,
		const Vector< Double > &	parameters
	)

Construct a projection which needs parameters.

The parameter vector must be the length of the required number of parameters.

casacore::Projection::Projection ( const Projection & other )

Copy constructor (copy semantics).

casacore::Projection::~Projection ( )

Destructor.

Member Function Documentation

static Bool casacore::Projection::isZenithal ( Projection::Type proj ) [static]

Is this projection a 'zenithal' projection.

static String casacore::Projection::name ( Projection::Type proj ) [static]

String casacore::Projection::name ( ) const

What is the type of this projection as a String (e.g.

"SIN").

Bool casacore::Projection::near	(	const Projection &	other,
		Double	tol = `1.0e-6`
	)			const

Comparison to fractional tolerance.

static uInt casacore::Projection::nMinParameters ( Projection::Type proj ) [static]

static uInt casacore::Projection::nParameters ( Projection::Type proj ) [static]

How many parameters does this projection have at most? What is the minimum number of parameters that have to be supplied? What are the parameter values?

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

Assignment (copy semantics).

const Vector< Double > & casacore::Projection::parameters ( ) const [inline]

Definition at line 219 of file Projection.h.

References parameters_p.

Projection::Type casacore::Projection::type	(	String &	ctypeLong,
		String &	ctypeLat
	)			const `[private]`

static Projection::Type casacore::Projection::type ( const String & name ) [static]

Turn a projection type name into a Type.

Returns N_PROJ if the projection is not known.

Projection::Type casacore::Projection::type ( ) const [inline]

What is the Type of this projection?

Definition at line 218 of file Projection.h.

References which_p.

void casacore::Projection::validate ( const Bool verbose = False ) [private]

Member Data Documentation

Vector<Double> casacore::Projection::parameters_p [private]

Definition at line 211 of file Projection.h.

Referenced by parameters().

Projection::Type casacore::Projection::which_p [private]

Definition at line 210 of file Projection.h.

Referenced by type().

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

casacore/coordinates/Coordinates/Projection.h