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change_polcconv
This IDL facility changes the coordinate convention in FITS file containing a polarised sky map.
The main effect is to change the sign of the U Stokes parameter,
and add/update the POLCCONV FITS header with either
COSMO or IAU value.
Location in HEALPix directory tree:
src/idl/fits/change_polcconv.pro
FORMAT IDL>
CHANGE_POLCCONV , File_In, File_Out [, /I2C, /C2I, /C2C, /I2I, /FORCE]
QUALIFIERS
-
File_In
- name of a FITS file to be read
-
File_Out
- name of a FITS file to be written, after modification of the
polarisation coordinate convention, if applicable
KEYWORDS
-
/I2C
- changes from IAU to COSMO coordinate convention
-if POLCCONV is not found or found with value 'IAU', it is
added/replaced with value 'COSMO', and the sign of the U stokes
parameter map is changed
-if POLCCONV already has value 'COSMO', File_In is copied
unchanged into File_Out
-
/C2I
- changes from COSMO to IAU coordinate convention
-if POLCCONV is not found or found with value 'COSMO', it is
added/replaced with value 'IAU', and the sign of the U stokes
parameter map is changed
-if POLCCONV already has value 'IAU', File_In is copied
unchanged into File_Out
-
/C2C
- does NOT change coordinate system
-if POLCCONV is found with value 'IAU', program will issue error
message and no file is written
-in all other case POLCCONV is set/added with value 'COSMO', but
data is NOT changed
-
/I2I
- does NOT change coordinate system
-if POLCCONV is found with value 'COSMO', program will issue error
message and no file is written
-in all other case POLCCONV is set/added with value 'IAU', but
data is NOT changed
-
/FORCE
- if set, the value of POLCCONV read from the FITS header is
ignored.
The sign of U is swapped (if used with /C2I or /I2C), and the
FITS keyword is updated accordingly.
DESCRIPTION
This routine will change the sign of the U Stokes parameters (and related
quantities, such as the TU and QU cross-correlations) and update the
'POLCCONV' FITS keyword where applicable.
The recognised format are:
- standard Healpix full sky polarised format
- cut sky Healpix polarised format
- WMAP 2nd year polarised format
RELATED ROUTINESThis section lists the routines related to change_polcconv
-
idl
- version 6.1 or more is necessary to run change_polcconv
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write_fits_cut4
- This HEALPix IDL
facility can be used to write a (polarised or unpolarised) cut sky map into a
FITS file.
-
read_fits_cut4
- This HEALPix IDL
facility can be used to read a (polarised or unpolarised) cut sky map from a
FITS file.
-
write_tqu
- This HEALPix IDL
facility can be used to write a polarised full sky map (with either the
standard Healpix format or the WMAP 2nd year format) into a
FITS file
-
read_tqu
- This HEALPix IDL
facility can be used to read a polarised cut sky map from a
FITS file
EXAMPLE:
Modify the file 'map_cosmo.fits', which was using the 'COSMO' convention for
polarisation coordinate convention into 'map_iau.fits' which uses the 'IAU' convention
Eric Hivon
2010-06-18
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