AIPS HELP file for VLBALOAD in 31DEC24
As of Fri Apr 26 10:41:18 2024
VLBALOAD: Procedure to load VLBA data from tape
INPUTS
INTAPE 0.0 9.0 Input tape drive number
DATAIN Disk file name
NFILES -999.0 9999.0 # of files to advance on tape
NCOUNT 0.0 9999.0 Number of files to load
(read from insert card)
OUTNAME Output file name
OUTDISK 0.0 15.0 Disk drive for output data
(0 => any)
DOUVCOMP -1.0 1.0 >0 => write compressed data
CLINT CL entry interval (min)
0 => 0.25 minute
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
file.
VLBALOAD is defined in the VLBAUTIL run file.
HELP SECTION
VLBALOAD
Type: Procedure
Use: VLBALOAD is a procedure that loads VLBA data from tape and may
be used for any data from the VLBA correlator. VLBALOAD also
runs TAMGR to merge redundant entries in the calibration tables
(GC, TY and PC) (this makes running VLBAMCAL unnecessary).
Type RUN VLBAUTIL to make the VLBALOAD procedure available.
Note that VLBALOAD permanently flags data with weights less than
0.7, which is fine for most data sets.
Adverbs:
INTAPE......The input tape drive number. This procedure assumes that
you have already mounted a FITS tape on this drive. Zero
defaults to tape drive number one.
DATAIN......48-character name of the disk file from which to read a
FITS file. It must be in the form
:
or
:::
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_
or
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.
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
them.)
NCOUNT......The number of files to read from the tape.
Zero defaults to a large number.
You can read the number of files on a VLBA
correlator tape from the listing inserted in the
tape case.
OUTNAME.....The name for the output files. The output files
will all be given the class UVDATA and assigned
distinct sequence numbers as needed.
OUTDISK.....The disk drive number for the output data. Choose
a disk with a large amount of space.
DOUVCOMP....If true (> 0.5) then output data will be
compressed which saves disk space at the expense
of losing some weighting information.
CLINT.......Calibration table interval in minutes. This should
normally be in the range 0.25 to 1.0. If <=0 then
0.25 is assumed.
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.
EXPLAIN SECTION
VLBALOAD: Procedure to load VLBA data from tape.
Documentor: Chris Flatters
Related Programs: FITLD, VLBAUTIL, VLBAMCAL, TAMGR
WHEN TO USE VLBALOAD
Use VLBALOAD to load all of the data from one or more VLBA export tapes into
a single AIPS file. Do not use VLBALOAD if you need to apply data selection
criteria or otherwise need more control over FITLD. As VLBALOAD permanently
flags data with weights less than 0.7, VLBALOAD is not appropriate for
data with a high fraction of low weights. VLBALOAD will also run TAMRG
to merge redundant entries in the calibration tables (GC, TY and PC).
This will only be run if there are calibration tables and more than 1
file has been loaded from tape. THIS IS A NEW FEATURE AND MAKES RUNNING
VLBAMCAL UNNECESSARY.
VLBALOAD is primarily intended for novice VLBA users and ensures that FITLD
is run with settings that make sense for most VLBA experiments. It is
also used in pipeline scripts.
LOADING DATA WITH VLBALOAD
1) If you have not already done so, type RUN VLBAUTIL to make the VLBALOAD
procedure available to you.
2) Examine the listings inserted in each of your tapes and sum the total
kilobytes for all of the tapes. This approximates the size of the
uncompressed data set that will be used in AIPS.
3) Type FREE and check the free blocks for each disk. You will need enough
disk space to hold at least 2 copies of your data in order to process it.
4) If there is at least one disk where the number of free blocks is more than
twice the uncompressed size of your data in kilobytes or if there are at
least two disks where the number of free blocks is greater than the
uncompressed size of your data in kilobytes then set DOUVCOMP to FALSE, set
OUTDISK to the number of a disk with a number of free blocks greater than
the uncompressed size of your data, and then proceed to Step 7, otherwise
continue with Step 5.
5) Divide the uncompressed size of your data by 3. This is a rough estimate of
the compressed size of your data. If there is at least one disk where the
number of free blocks is more than twice the compressed size of your data
or if there are at least two disks where the number of free blocks is
greater than the compressed size of your data then set DOUVCOMP to TRUE,
set OUTDISK to the number of a disk with a number of free blocks greater
than the uncompressed size of your data, and then proceed to Step 7,
otherwise continue with Step 6.
6) If you have reached this point then you do not have sufficient disk space
to reduce you data. You either need to delete some old files or to find a
machine with more disk space.
7) Choose a calibration table interval and specify it as CLINT. One minute
will be suitable for most experiment. Higher frequency bands may require
shorter intervals. Consult a more experienced VLBA user if you are not sure
what to use.
8) Specify a name for your output data files. The OBSCODE is often a good
choice.
9) Specify the tape drive that you will be using as INTAPE.
10) Insert the first tape in your drive and mount it using the MOUNT verb.
11) In most cases set NFILES to 0
12) Set NCOUNT to the number of files listed on the insert and then type
VLBALOAD.
13) When the procedure finishes and the AIPS prompt reappears, dismount the
tape.
14) If you have more than one tape then repeat steps 10 through 12 for each
remaining tape.
WHAT TO DO NEXT
After loading the data, you should normally run VLBAFIX to sort the data etc,
if necessary.