/usr/include/casacore/fits/FITS/FITSSpectralUtil.h is in casacore-dev 2.2.0-2.
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//# Copyright (C) 2002
//# Associated Universities, Inc. Washington DC, USA.
//#
//# This library is free software; you can redistribute it and/or modify it
//# under the terms of the GNU Library General Public License as published by
//# the Free Software Foundation; either version 2 of the License, or (at your
//# option) any later version.
//#
//# This library is distributed in the hope that it will be useful, but WITHOUT
//# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
//# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
//# License for more details.
//#
//# You should have received a copy of the GNU Library General Public License
//# along with this library; if not, write to the Free Software Foundation,
//# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
//#
//# Correspondence concerning AIPS++ should be addressed as follows:
//# Internet email: aips2-request@nrao.edu.
//# Postal address: AIPS++ Project Office
//# National Radio Astronomy Observatory
//# 520 Edgemont Road
//# Charlottesville, VA 22903-2475 USA
//#
//#
//# $Id$
#ifndef FITS_FITSSPECTRALUTIL_H
#define FITS_FITSSPECTRALUTIL_H
#include <casacore/casa/aips.h>
#include <casacore/measures/Measures/MDoppler.h>
#include <casacore/measures/Measures/MFrequency.h>
namespace casacore { //# NAMESPACE CASACORE - BEGIN
class RecordInterface;
class String;
template<class T> class Vector;
class LogIO;
// <summary>
// A class with static functions to help deal with FITS spectral axes.
// </summary>
// <use visibility=export>
// <reviewed reviewer="Eric Sessoms" date="2002/08/19" tests="tFITSSpectralUtil.cc">
// </reviewed>
// <prerequisite>
// <li> General knowlege of FITS, FITS keywords, and FITS coordinate
// conventions is assumed.
// <li> Presumably you are using this in conjuction with the
// <linkto class=FITSKeywordUtil>FITSKeywordUtil</linkto> class
// to get or set the FITS coordinate axis information.
// </prerequisite>
// <etymology>
// This is a collection of static utility functions for use with
// FITS spectral axes.
// </etymology>
// <synopsis>
// This class provides functions to extract information from a FITS
// header about the spectral axis, to setup a FITS header with
// appropriate information for the spectral axis, and to translate
// to and from the MFrequency reference frame codes and their FITS
// equivalents.
// It is never necessary to construct a FITSSpectralUtil, just use the
// static functions to help handle FITS Spectral axes.
// </synopsis>
//
// <example>
// <srcblock>
// Record rec;
// ... extract the FITS keyword values into rec using FITSKeywordUtil
// Int whichAxis;
// Double refPix, refFreq, freqInc, restFreq;
// Vector<Double> freqs;
// MFrequency::Types refFrame;
// MDoppler::Types veldef;
// LogIO logger;
// FITSSpectralUtil::fromFITSHeader(whichAxis, refPix, refFreq,
// freqInc, freqs, refFrame, veldef, logger, rec);
// </srcblock>
// </example>
//
// <motivation>
// This is designed to be used after the keywords have been extracted from
// the FITS file using the <linkto class=FITSKeywordUtil>FITSKeywordUtil</linkto>
// class. Extracting spectral axis and related information requires detailed
// knowledge of FITS conventions that this class strives to encapsulize.
// </motivation>
//
// <todo asof="2011/11/30">
// <li> General usage of units for frequency and velocity in "fromFITSHeader"
// (currently only implemented for wavelength)
// </todo>
class FITSSpectralUtil
{
public:
// Get information about the spectral axis from a record containing the
// FITS axis information. Usually this will be from a FITS header using,
// for example, the FITSKeywordUtil::getKeywords method.
// referenceFrequency and deltaFrequency give the best
// possible linear frequency scale. prefix is the first character in the
// set of keywords describing the axes (e.g. crpix, crval, ctype - the prefix is
// 'c'). If oneRelative is False, the returned referenceChannel is decrimented
// from that found in header by 1. The naxis keywords are used to determine
// the output length of the freqs vector.
// This method returns False if:
// <ul>
// <li> no spectral axis is found. The freqs vector will have a length of zero.
// <li> The expected set of axis description keywords is not found.
// <li> The spectral axis is FELO but there is no rest frequency (making it
// impossible to convert to frequency and construct a freqs vector).
// <li> The combination FELO and RADIO is used (which does not make sense).
// <li> The combination VELO and OPTICAL is used (not yet implemented).
// </ul>
static Bool fromFITSHeader(Int &spectralAxis,
Double &referenceChannel,
Double &referenceFrequency,
Double &deltaFrequency,
Vector<Double> &frequencies,
MFrequency::Types &refFrame,
MDoppler::Types &velocityPreference,
Double &restFrequency,
LogIO &logger,
const RecordInterface &header,
char prefix = 'c',
Bool oneRelative=True);
// Nearly the inverse of fromFITSHeader. This returns parameters which could
// be used in filling in a header record with appropriate values for
// the spectral axis given the arguments after the logger.
// The alternate axis description values are set when sufficient information is available.
// If they have been set, haveAlt will be set to True.
// <ul>
// <li> Note that the output arguments after "haveAlt"
// should not be written to the FITS header unless haveAlt is true.
// <li> Note that restfreq is both an input and an output. If there is no
// rest frequency, set it to be <=0 on input.
// </ul>
// If preferVelocity is True, the
// axis description parameters will be set to those appropriate for
// a velocity axis given the referenceFrame, and velocityPreference
// if possible.
// If preferWavelength is True, the
// axis description parameters will be set to those appropriate for
// a wavelength axis given the referenceFrame if possible.
// The two preferences cannot be True at the same time.
// If airWavelength is True, the
// axis description parameters will be set to those appropriate for
// an air wavelength axis given the referenceFrame if possible.
// This parameter has an effect only if preferWavelength is True.
// This method always returns True.
static Bool toFITSHeader(String &ctype,
Double &crval,
Double &cdelt,
Double &crpix,
String &cunit,
Bool &haveAlt,
Double &altrval,
Double &altrpix,
Int &velref,
Double &restfreq,
String &specsys,
LogIO &logger,
Double refFrequency,
Double refChannel,
Double freqIncrement,
MFrequency::Types referenceFrame,
Bool preferVelocity = True,
MDoppler::Types velocityPreference = MDoppler::OPTICAL,
Bool preferWavelength = False,
Bool airWavelength = False,
Bool useDeprecatedCtypes = False);
// Convert a reference frame tag (typically found as the characters
// after the first 4 characters in a ctype string for the
// frequency-like axis) to a MFrequency::Types value.
// A velref value (used in AIPS images to alternatively record
// the velocity reference frame) may also optionally be supplied.
// If tag is empty, velref will be used if it is >= 0.
// This function returns False if:
// <ul>
// <li> The tag is not empty but is unrecognized.
// <li> The tag is empty and velref is unrecognized.
// <li> The tag is empty and velref is < 0 (no velref was supplied).
// </ul>
// The default value (set when the return value is False) is TOPO.
static Bool frameFromTag(MFrequency::Types &referenceFrame,
const String &tag,
Int velref=-1);
// Construct a reference frame tag from the given referenceFrame
// An appropriate velref value is also constructed (this may need
// to be adjusted by +256 if the velocity definition is radio before
// being used in a FITS file). This returns False if the
// reference frame is not recognized. The value of tag defaults
// to "-OBS".
static Bool tagFromFrame(String &tag, Int &velref,
MFrequency::Types referenceFrame);
// Construct a SPECSYS keyword value from the given referenceFrame
// This returns False if the reference frame is not recognized.
// The value of tag defaults to "TOPOCENT".
static Bool specsysFromFrame(String &specsys,
MFrequency::Types referenceFrame);
static Bool frameFromSpecsys(MFrequency::Types& refFrame, String& specsys);
// The refractive index of air (argument can be vacuum wavelength or airwavelength)
// according to Greisen et al., 2006, A&A, 464, 746.
// If vacuum wavelength is used there is an error of the order of 1E-9.
// Argument must be in micrometers!
static Double refractiveIndex(const Double& lambda_um);
};
} //# NAMESPACE CASACORE - END
#endif
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