As of Mon Jul 15 12:41:02 2024

FITLD: Task to store an image or UV data from a FITS tape


INTAPE            0.0       9.0    Input tape drive # (0 => 1)
NFILES        -9999.0    9999.0    # of files to advance on tape
DATAIN                             Disk file name
OUTNAME                            File name (name)
OUTCLASS                           File name (class)
OUTSEQ           -1.0    9999.0    File name (seq. #)
                                      0 => highest unique number
                                        => matching (on VLBA)
                                     -1 => FITS tape value
OUTDISK           0.0       9.0    Disk drive # (0 => any)
OPTYPE                             Type of data to load,
                                   '  ' => all types
                                   'UV' => UV data
                                   'IM' => images
NCOUNT            0.0    9999.0    Number of files to load.
DOTABLE          -1.0       1.0    True (1.0) means load tables
                                   for images.
DOUVCOMP         -1.0       1.0    >0 => compressed data (FITS)
DOCONCAT         -1.0        1.0   >0 -> if VLBA correlator data
                                   append data to existing
                                   files, or if no appropriate
                                   files exist create a new file
                                   and append all data to that
DOKEEP           -1.0       1.0    > 0 -> keep fully flagged
                                   data records
NPIECE            0.0      90.0    Maximum uv table piece to
                                   load (ignored for tape unless
                                   NCOUNT = 1)
ERROR            -1.0       3.0    >= 2 -> do not use AIPS
                                   history in the FITS file
                                   Following adverbs are useful
                                   only when reading VLBA IDI
                                   distribution tapes.
CLINT                              CL entry interval (min)
                                   0 => 1 minute.
SOURCES                            Source list to accept.
QUAL            -10.0              Source qualifier -1=>all
TIMERANG                           Timerange selected
BCHAN             0.0     8192.0   Lowest spectral channel
                                   number to select in each IF.
ECHAN             0.0     8192.0   Highest spectral channel
                                   number to select in each IF.
BIF               0.0      100.0   Lowest IF number 0=>1
EIF               0.0      100.0   Highest IF number 0=>all
DIGICOR          -1.0        4.0   Controls the application of
                                   the VLBA and DIFX correlator
                                   digital correction.
                                   0,1,3 => perform corrections
                                   2,4 => perform cross-power
                                     corrections, do total-power
                                     only if zero padding used.
                                   -1 => do NOT perform
                                   3,4 => do even if not VLBA
                                   SEE HELP for more details
REFDATE                            Reference date. 'yyyymmdd'
                                      before or = the obs date
                                      ' ' => the obs date
SELBAND                            Bandwidth to select (kHz)
SELFREQ                            Frequency to select (MHz).
                                   See HELP.
FQTOL                              Frequency tolerance assigned
                                   to SELFREQ, FITLD will select
                                   data with freq. of SELFREQ
                                   +/- FQTOL.
                                   The unit of FQTOL is kHz.
                                   <=0 => 10 kHz
WTTHRESH                           Flagging threshold based on
                                   weights. See HELP.
                                   0 => no flagging
                                   1 => will flag ALL data
DOWEIGHT                           > 0 => scale weights by
                                     (Int time)*(bandwidth)
OPCODE                             Specify if wish to keep VT
                                   (VLBA Tape Statistics) table
                                   and other tables.  See HELP.
                                   '  ' => do not save tables
ANTNAME                            List antenna station names in
                                   desired order (IDI data only)
                                   'VLBA', 'VLITE' are special


Type: Task
Use:  FITLD loads both maps and UV data from tape (or disc) to disc. It
      will only load FITS files, if any other type of file exist on the
      tape the task will fail, so users must skip over non-FITS files.
      The aim of this task is to read, in one pass, a tape written by
      FITTP or FITAB.  However a user may specify that all 'UV' files
      are to be loaded, or all map files, or (default) all types of
      FITS file.  If IMAGE extensions are present, they are written to
      separate catalog entries, but all TABLES are attached to the
      primary catalog entry.  They may only occur with a real or empty
      image in the main FITS HDU.

      FITLD reads standard images and uv data from FITS files and also
      translates FITS-IDI files.  This last is normally written by
      correlators rather than post-processing software and requires
      additional adverbs not honored by the other portions of FITLD.

      Until the end of July 1999, UV data sets written out with FITAB,
      read back in with UVLOD or FITLD, processed, and then written out
      with FITTP could contain AIPS history records which will define
      the data set falsely to the standard reading tasks in AIPS.  If
      you attempt to read a data set or image with FITLD (NOT a VLBA
      correlator data set) and encounter error 4 (premature end of file)
      or other failure, try reading the FITS data set with PRTTP with
      ERROR set to 2.  If this works, use UVLOD for UV data and IMLOD
      for images with ERROR=2.

      FITLD (and IMLOD, UVLOD, PRTTP, TPHEAD) now understand and
      interpret the standard world coordinate system keywords CDi_j
      and PCi_j.  They are used if possible and problems reported.

       Data from MeerKAT will automatically have the polarizations
       swapped, unless the FITS file reveals that the data have already
       been in AIPS.. If you do not want this you will have to run SWPOL
       after UVLOD.
  INTAPE......The input tape drive #.  0 => 1.
  NFILES......# of files to skip on tape before reading data.  For
              example, 1 => start of next file, -1 => start of previous
              file.  0 => no tape movement at all.  (AIPS verbs AVFILE
              plus TPHEAD allow you to position and check the tape in
              advance; be sure to reset NFILES to 0 for FITLD after
  DATAIN......48-character name of the disk file from which to read a
              FITS file.  It must be in the form
              where  is the remote computer name,  is the
              environment variable (logical name) for the disk area in
              which the file named  is stored.   is
              usually omitted when the file is local to the current
              computer.  If DATAIN is not found, the task will try
              DATAIN with the character 1 appended.
              Beginning 2003-Oct-16 FITLD can read more than one disk
              file at a time.  In that case, they must all have the
              same name except that the last letter(s) are the
              sequence number 1 through NCOUNT with no leading zeros.
              DATAIN must give the base name only, omitting the
              sequence number.  Then either
                    DATAIN = 'MYDATA:file_
                    DATAIN = 'MYDATA:file_1
              can access files in $MYDATA named file_1, file_2,
              file_3, etc.  Note that this is similar to the pieces of
              a FITS pieced UV-table data set, but only one UV-table
              data set may be read at a time.
  OUTNAME.....The output filename (name).  Standard behavior with
              default = the original file name (FITS), the source name,
              or 'NONE'.
  OUTCLASS....The output filename (class).  Standard behavior with
              default = the original map class (FITS) or a class of the
              form 'STYP  ', where S = (I, Q, U, V) Stokes parameter of
              the image and TYP = (BEM, CLN, MAP) for a beam, clean map,
              or anything else.  Special combination images (OPTD et
              al.) are also recognized.
  OUTSEQ......The output filename (seq #).  0 => Find the lowest number
              which produces a unique mapname.  -1 => use the sequence
              number on the tape (if any - works only on tapes written
              by FITTP).  SEE ALSO the remarks below under DOCONCAT.
  OUTDISK.....The disk drive #.  0 => highest with space
  OPTYPE......The type of data files to load, ' ' (default) => load uv
              and images; 'UV' => load uv files only; 'IM' => load
              images only.
  NCOUNT......The number of consecutive files to load from tape or
              disk.  0 -> 10000 for tape data, 0 -> 1 for disk FITS
              files, but it is better to give a correct number to
              allow the program to manage messages, file status, etc.
              If you want to load only up to NPIECE pieces of a uv
              table set, then NCOUNT must be 1 (or 0 if disk since
              that defaults to 1).  Note that the multiple pieces of a
              uv-table set are counted as 1 for the purposes of NCOUNT
              (but not NFILES).
  DOTABLE.....True (1.0) means load all tables. (FITS images only, all
              tables are loaded for UV data and IDI files).
  DOUVCOMP...If true (DOUVCOMP > 0) the output data is written in
             compressed format which can result in a substantial
             reduction in disk space needed.  This causes some loss of
             spectral dynamic range and allows one bad channel value
             to destroy all the good data; the numbers are stored as
             integers of value -32767 to 32767.  Real differences in
             weights between IFs, polarizations, and spectral channels
             within a record are also lost.  Only used for FITS files
             of the random-groups type (e.g. written by FITTP or CASA
             exportuvfits) and those written in the IDI convention for
             binary tables.  Binary tables such as those written by
             FITAB have the compression selected by the compression
             state of the table.  Not used for images.
  DOCONCAT...If true (>0) and the input data are VLBA binary tables
             (IDI directly from the correlator) then data are to be
             appended to an existing file if possible.  Possible
             output files can be selected by OUTNAME, OUTDISK and
             OUTSEQ.  Use this option with CAUTION; it is REQUIRED (to
             be true) if you wish to concatenate the data from
             multiple files being read in the same execution of FITLD
             for VLBA correlator data.  (UV table pieces from FITAB
             are concatenated to each other even if DOCONCAT is false.)
             If DOCONCAT is false and OUTSEQ is specified, FITLD will
             fail at the start of file 2.  If DOCONCAT is false and
             OUTSEQ is not specified, then FITLD will make separate disk
             files for each tape file.  These disk files may be
             concatenated later with DBCON, but perhaps only after
             they have been MATCHed.  FITLD will write one or, if it
             finds data that do not match in e.g. number of channels,
             more output files.  If DOCONCAT is TRUE then FITLD will
             look over all files matching the OUTNAME, OUTCLAS,
             OUTSEQ, OUTDISK parameters to try to find one that it can
             append data to.  If it does not it will create one based
             on these name parameters.  That will generally fail if
             OUTSEQ is specified.  Thus, for DOCONCAT true, set
             OUTSEQ=0.  Be very careful if specifying ANTNAME with
             DOCONCAT true.
  DOKEEP.....> 0 -> keep any fully flagged vis records.  Otherwise
             they are not copied from the input file.  They are
             counted and reported in any case.
  NPIECE.....Maximum piece number to read in a multi-piece uv-table FITS
             data set.  0 => maximum in the data.  Note, if NCOUNT > 1,
             NPIECE is set to 999 by FITLD.
  ERROR......>= 2 => do not parse AIPS history cards found in the FITS
             header.  Do not use this option until you have tried IMLOD
             without it.  If you get mysterious errors (usually error 4
             which implies premature end of file), then try IMLOD with
             ERROR set to 2.  For a period of time, UV data sets written
             out with FITAB, read back in, processed, and then written
             out with FITTP could have so many AIPS history records in
             their header as to cause IMLOD to read the data wrongly.
             This can also occur when AIPS data are written to another
             package and then brought back to AIPS.
        The following adverbs apply only to FITS-IDI data files
        which generally are written by VLB correlators rather than
        post-processing software.  The VLITE project of the VLA also
        uses VLB-like files.
  CLINT......IDI only: To define the interval between CL entries for
             antennas for data from the VLBA correlator only.  This
             defines the fundamental time-scale for calibration, 1
             minute is a good value for most frequencies. Shorter
             intervals may be relevant for high frequency programs.
  SOURCES....IDI only: Source list.  List of sources to accept from
             the VLBA distribution tape (or files).
  QUAL.......IDI only: Only sources with a source qualifier number in
             the SU table matching QUAL will be used if QUAL is not -1.
  TIMERANG...IDI only: Range of UTC times to be read wrt the first day
             number in the first file read. 0=>all.
  BCHAN......IDI only: First spectral channel number to select from
             each IF. 0=>1.
  ECHAN......IDI only: Highest spectral channel number to select from
             each IF.  0=>all higher than BCHAN.
  BIF........IDI only: First IF to copy. 0=>1
  EIF........IDI only: Highest IF to copy. 0=>all higher than BIF.
             WARNING: IF selection will work differently in FITLD
             where it is based on the input IF numbers and in later
             tasks where it is based on IF numbers reordered by FITLD
             to frequency order.  These two selections will be the
             same only if the data from the correlator are in
             increasing frequency order.
  DIGICOR....IDI only: Data processed in digital correlators such as
             the VLBA correlator and DiFX are affected by a variety of
             phenomena that we collectively refer to as digital
             effects. FITLD is able to apply the corrections needed to
             scale the data to the values that would be returned by a
             purely analogue correlator.  DIGICOR = -1 will turn off
             the application of these correction, DIGICOR = 0 or 1
             will apply them to both cross and total power, DIGICOR =
             2 will apply the corrections to cross-power and only to
             total power if zero-padding was used in the correlator.
             The latter case is designed to deal with a situation in
             which the total-power spectrum is dominated by multiple,
             strong spectral lines.  In that case, if zero-padding was
             not used, the reconstructed total-power spectrum, after
             an FFT, is inaccurate at some level. In all continuum
             cases DIGICOR = 1 should be the default.  In nearly all
             line cases DIGICOR = 1 is fine. only if the Tant in the
             line is about equal to the Tsys should DIGICOR = 2 be
             used.  One word of caution, for data correlated prior to
             Aug 1 1994 the correlator was incorrectly scaling the
             data by a factor of 1.57 (i.e. PI/2) . So for that data,
             DIGICOR can be used but a BFACTOR of 0.6369 (i.e. 1/1.57)
             should be applied in APCAL or to the final images.
             Unfortunately FITLD had no knowledge of the date of
             correlation so cannot perform this correction.  The code
             detects data from the DiFX correlator and applies a
             different (1.0) saturation correction in that case.
             Actually, 1.0 is used for all but the VLBA (array=VLBA
             and correlat ' ' or 'VLBA'),
             ****  FITLD will do corrections for arrays other than
             ****  VLBA only if DIGICOR is set to 3 or 4.
             If the keyword VANVLECK appears in the FITS header with
             value 1, then the "van Vleck" like correction has already
             been applied to the visibilties by DiFX and that portion
             of the digital correction will be set to 1.0 (i.e. no
  REFDATE....IDI only: Reference date 'yyyymmdd' ('dd/mm/yy' accepted
             but deprecated),  ' ' => first found
             Better get it right - a date after the reference date in
             the data will cause the data to fail to load.
  SELBAND....IDI only: Bandwidth of data to be selected. If more than
             one IF is present SELBAND is the width of the lowest
             frequency IF required.  Units = kHz, 0=> all
  SELFREQ....IDI only: Frequency of data to be selected. If more than
             one IF is present SELFREQ is the frequency of the lowest
             frequency IF required. FITLD will sort the IF channels
             into increasing frequency order as the data are read from
             the tape so all selection will be performed on the
             frequency and bandwidth values of the output IF 1.
             Units = MHz, 0=> all
  FQTOL......IDI only: The frequency tolerance used in selecting data
             using SELFREQ. Data whose output IF 1 frequency lies in
             the range SELFREQ +/- FQTOL will be read.  Units = kHz,
             =< 0 => 10kHz
  WTTHRESH...IDI only: Weight based flagging threshold. If WTTHRESH
             > 0 the weights for each visibility are examined.  If
             weights for all IFs are =< WTTHRESH the visibility record
             is flagged. The flagging is permanent, i.e. the record is
             not copied to the output file.
             If a weight of some IFs (not all) =< WTTHRESH such
             visibilities are recorded, but the weight of these IFs is
             put to zero (flagged).  Input weights lie between 0 and
             1. If you wish to apply weight based flagging a suggested
             value for WTTHRESH is 0.8. A value of 0 switches off the
  DOWEIGHT...> 0 => (IDI only) scale the weights by the product of the
                    integration time (sec) and the channel bandwidth
                    (Hz).  This will make the data weights be sensible
                    when the amplitude calibration is applied, i.e.
                    more or less 1/sigma^2 in 1/Jy^2.
             <= 0 => Data weights stay as they are in the IDI file.
                    After calibration they will be on the order of
  OPCODE.....IDI only: By default, the input tables that are
             translated into AIPS tables are all removed and the large
             VT (VLBA Tape Statistics) table is neither translated nor
             saved.  If you wish to keep the former and/or latter enter:
             'VT'   => Keep VT tables, not the rest
             'ALL'  => Drop VT tables, keep rest
             'VALL' => Keep VT and other tables
  ANTNAME....With FITS-IDI files, the antennas acquire antenna numbers
             in the order in which they are encountered in reading
             the input files.  To select a specific order (to force
             the same antenna numbers with different data sets), you
             may specify the antenna/station names in the desired
             order.  The special string VLBA is converted to 10 names
             'BR', 'FD', 'HN', 'KP', 'LA', 'MK', 'NL', 'OV', 'PT',
             and 'SC'.  Any antenna not in the list will be added to
             the end of the list as it is encountered.
             The special string VLITE will generate the list 'V0',
             If you are concatenating, make sure this list applies to
             the pre-existing file.  The list will be used during
             concatenation if it can be.  Note that lists starting
             with VLBA or VLITE will only look for those antennas
             during concatenation.  Any others in ANTNAME will be


FITLD: Task to load FITS format data
Documentor: Chris Flatters


Disk file reading: DATAIN

To read multiple disk files in one pass of FITLD, the file names must
all be predictable from the user supplied value of DATAIN.  This
requirement has led to the requirement that they be named with a
consecutive postfix number beginning with 1.  It may seem onerous to
have to do this, so we suggest using link files.  Thus 4 disk files of
consecutive VLBA correlator data may be linked to a simple name in the
local directory ($MYWORK) by

primate<142>$ ln -s /home/euro/aipsdvlp/WB/AO-0/32400001.FITS Lorant_1
primate<143>$ ln -s /home/euro/aipsdvlp/WB/AO-0/32410001.FITS Lorant_2
primate<144>$ ln -s /home/euro/aipsdvlp/WB/AO-0/32420001.FITS Lorant_3
primate<145>$ ln -s /home/euro/aipsdvlp/WB/AO-0/32430001.FITS Lorant_4

Then, inside AIPS, one sets
      NCOUNT = 4; DATAIN = 'MYWORK:Lorant_
where you should note (a) DATAIN= is the last command on the line and
is typed with no close quote so that the case is preserved, (b) the
number 1 may be left off the name (FITLD will append it), and (c) the
environment vaiable $MYWORK must be known before AIPS is started and
is typed with a colon following but no $.



FITLD will load flags, gain curves, system temperature data, and
pulse-cal data from VLBA format FITS files. These data will be
loaded into version 1 of the FG, GC, TY, and PC tables

If several input files are concatenated into one AIPS file then
the FG, GC, TY, and PC tables will contain the calibration data
from all of the inputs files that were concatenated. This may
lead these tables containing duplicated records.

I recommend that you remove all of the duplicate records in the
GC, TY, and PC tables after you have loaded all of the data for
a given experiment using the procedure MERGECAL (see HELP


Reference dates.

FITLD assumes that the reference date for the data loaded from
FITS-IDI files is the first reference date encountered in any
of the tables in the file. If the file conforms the the table
ordering conventions in AIPS Memo 102 then this should be the
reference date for the ARRAY_GEOMETRY table for the first
array. This is normally the correct reference date.

If any table has a reference date (RDATE) earlier than that
chosen by FITLD or if data occur before 0h on the chosen
reference date then AIPS may not be able to handle the data
output by FITLD.

It is also possible for problems to occur if the first table
in the file that has an RDATE keyword is not an ARRAY_GEOMETRY
table and the value of that keyword differs from the RDATE of
of the first ARRAY_GEOMETRY table since the reference date
will not then be the same as the reference date for subarray
1 as is assumed in some parts of AIPS.

This adverb has been removed and made always true.  It is turned off
for correlators other than the VLBA.
  DELCORR....This parameter determines whether the second order
             amplitude corrections caused by delay decorrelation
             in the VLBA correlator can be applied after fringe
             fitting or not. These corrections are necessary for
             obtaining extremely high dynamic range images. If
             they are not applied excellent images can still be
             obtained. The corrections are applied when a CQ
             table is attached to the data, the CQ table
             contains information required to perform the
             correction - see AIPS Memo 90 by Athol Kemball for
             more details. Under some circumstances (e.g.
             spectral averaging in the correlator on data that
             contains narrow spectral lines) the assumptions
             under which the 2nd-order corrections can be
             applied are false. In that case the CQ table should
             not be generated.
             DELCORR = -1 => do not generate CQ table
             DELCORR >= 0 => generate CQ table.