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write_fits_cut4
This IDL facility writes out a cut sky HEALPix map into a FITS file according to
the HEALPix convention. The format used for the
FITS file follows the one used for Boomerang98 and is adapted from
COBE/DMR. This routine can be used to store polarized maps, where the
information relative to the Stokes parameters I, Q and U are placed in extension
0, 1 and 2 respectively by successive invocation of the routine. Location in HEALPix directory tree:
src/idl/fits/write_fits_cut4.pro
FORMAT IDL>
WRITE_FITS_CUT4 , File, Pixel, Signal [, N_Obs, Serror,
COORDSYS=,
EXTENSION=,
HDR=,
/NESTED,
NSIDE=,
ORDERING=,
/POLARISATION,
/RING,
UNITS=,
XHDR=]
QUALIFIERS
-
File
- name of a FITS file in which the map is to be written
-
Pixel
- (LONG or LONG64 vector),
index of observed (or valid) pixels
-
Signal
- (FLOAT or DOUBLE vector, same size as Pixel),
value of signal in each observed pixel
-
N_Obs
- (LONG or INT or LONG64 vector, Optional, same size as Pixel),
number of
observation per pixel.
If absent, the field N_OBS will take a value of 1 in the output file.
If set to a scalar constant, N_OBS will take this value in the
output file
-
Serror
- (FLOAT or DOUBLE vector, Optional, same size as Pixel)
rms of signal in pixel, for white noise,
this is
If absent, the field SERROR will take a value of 0.0 in the output file.
If set to a scalar constant, SERROR will take this value in the
output file
KEYWORDS
-
COORDSYS=
- (optional),
if set to either 'C', 'E' or 'G', specifies that the
Healpix coordinate system is respectively Celestial=equatorial,
Ecliptic or Galactic.
(The relevant keyword is then added/updated in the extension
header, but the map is NOT rotated)
-
EXTENSION=
- (optional),
(0 based) extension number in which to write data. default:0.
If set to 0 (or not set) a new file is written from scratch.
If set to a value
larger than 1, the corresponding extension is added or
updated, as long as all previous extensions already exist.
All extensions of the same file should use the same ORDERING,
NSIDE and COORDSYS.
-
HDR=
- (optional),
String array containing the information to be put in
the primary header.
-
/NESTED
- if set, specifies that the map is in the NESTED ordering
scheme
see also:Ordering and Ring
-
NSIDE=
- (optional),
scalar integer, HEALPix resolution parameter of the
data set. The resolution parameter should be made
available to the FITS file, either thru this
qualifier, or via the header (see XHDR).
-
ORDERING=
- (optional),
if set to either 'ring' or 'nested' (case un-sensitive),
specifies that the map is respectively in RING or NESTED
ordering scheme
see also:Nested and Ring
The ordering information should be made
available to the FITS file, either thru a combination
of Ordering/Ring/Nested, or via the header (see XHDR).
-
/POLARISATION
- specifies that file will contain the I, Q and U polarisation
Stokes parameter in extensions 0, 1 and 2 respectively, and sets the
FITS header keywords accordingly
-
/RING
- if set, specifies that the map is in the RING ordering
scheme
see also:Ordering and Nested
-
UNITS=
- (optional),
string describing the physical units of the data set (only applies
to Signal and Serror)
-
XHDR=
- (optional),
String array containing the information to be put in
the extension header.
DESCRIPTION
RELATED ROUTINESThis section lists the routines related to write_fits_cut4
-
idl
- version 6.1 or more is necessary to run write_fits_cut4
-
read_fits_cut4
- This HEALPix IDL facility can be used to read in maps
written by write_fits_cut4 .
-
write_fits_cut4,
write_fits_map
-
write_tqu,
write_fits_sb
- HEALPix IDL routines to write cut-sky maps, full-sky maps, polarized full-sky maps and
arbitrary data sets into FITS files
-
sxaddpar
- This IDL routine (included in HEALPix package) can be used to update
or add FITS keywords to the header in HDR and XHDR
EXAMPLE # 1:
writes in 'map_cut.fits' a FITS file containing the temperature measured in a
set of HEALPix pixel.
EXAMPLE # 2:
writes in 'tqu_cut.fits' a FITS file with three extensions, each of them containing
information on the observed pixel, the measured signal, the number of
observations and noise per pixel, for the three Stokes parameters I, Q and U
respectively. The HEALPix ring ordered scheme and the resolution
is assumed.
Eric Hivon
2010-06-18
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