AIPS HELP file for FITAB in 31DEC24
As of Wed Apr 24 7:05:07 2024
FITAB: Task to write maps or uv data as tables on a FITS tape
INPUTS
DOALL -1.0 1.0 1 (T) do all, -1 (F) do 1st.
INNAME Image name(name). Standard.
INCLASS Image name(class). Standard.
INSEQ 0.0 9999.0 Image name(seq. #).
INDISK 0.0 9.0 Disk drive #. 0 => any
INTYPE File type. Blank => any
OUTTAPE 0.0 9.0 Tape drive #. 0 => 1
DATAOUT
Disk file name
DOEOT -1.0 1.0 1 (T) go to end tape first.
FORMAT 0.0 4.0 tape format: 0 => 3.
1 for 16-bit integer
2 for 32-bit integer
3 for 32-bit IEEE
floating point
4 for 8-bit integer
BLOCKING 0.0 10.0 tape blocking factor (<= 10)
QUANTIZE 0.0 Quantize images written
***** BE CAREFUL!!!
DOUVCOMP -1.0 1.0 > 0 => write compressed form
of uv data in output tables
NPIECE 0.0 90.0 Break uv data into NPIECE
pieces
BDROP 0.0 90.0 Don't write the first BDROP
pieces
CATNO Limit range of DOALL
HELP SECTION
FITAB
Type: Task
Use: FITAB converts the standard header and map or uv data and writes
it on an output tape in the FITS format. The first or all uv or
image files that match the input parameters can be written. The
tape is left following the End-of-file mark which terminates the
last file written. All Clean Components extension files for maps
or ANtenna files for uv data will be written with the image in a
standard binary TABLES format (following the image or itself in
the file). Other tables-format extension files will also be
written.
FITAB differs from FITTP in that it writes uv data as a binary
table rather than a "random-groups" structure. This allows it to
be written in a compressed format that is essentially the same as
compressed uv data on disk. It also allows the data if it is in
time order to be written as multiple files each covering no more
than a specified time interval.
*****************************************************************
FITAB IS NEW IN 15APR99 AND ITS UV-DATA OUTPUT CANNOT
BE READ IN TO EARLIER VERSIONS OF AIPS
*****************************************************************
Adverbs:
DOALL......True (> 0) means do all files matching the input
parameters, false (<= 0) means do the 1st match
only.
INNAME.....The input image name (name). Standard defaults.
INCLASS....The input image name (class). Standard defaults.
INSEQ......The input image name (seq. #). 0 => any if DOALL
is true, 0 => highest if DOALL is false.
INDISK.....The input disk unit #. 0=> search all disks in
order for file meeting the other criteria.
INTYPE.....The input data type (MA or UV or ' ' for either)
OUTTAPE....The output tape unit #. 0=> 1.
DATAOUT....The name of a disk file into which to write. If blank then
write to tape. If output is to a disk file, only 1 file
can be written (DOALL=-1). If the data set is broken into
multiple pieces, then the file name will have a character
appended to it representing the piece number. The name is
limited to 48-characters and 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 to be stored.
is usually omitted when the file is local to the current
computer.
DOEOT......True (> 0) means to advance the tape to the end of
information (double EOF) before writing, false means write
wherever the tape is now positioned. Note: set DOEOT true
ONLY if you think that there are already FITS data files on
the tape AND if you wish to preserve them.
FORMAT.....Code to tell what format to be used in writing the main
image data portion of the file as
1 for 16-bit integers - only images
2 for 32-bit integers - only images
3 for 32-bit IEEE floating point - images
4 for 8-bit integers - only images
Default: 0 => 3.
If you want to import your FITS data into another system,
make sure that it is able to read the format that you have
selected. Tables including all UV data are written in a
format appropriate to their columns. The UV visibilities
are in a format controlled by DOUVCOMP.
BLOCKING...Code to tell what blocking factor to be used in writing the
whole file Default: 0 => 10.
Considerations: (a) blocking factor <= 10.
(b) Blocking is ignored when writing to disk
rather than tape.
(c) Larger blocks use fewer I/O operations
making tape reads and writes more efficient.
QUANTIZE...<= 0 => write the output image with the maximum possible
accuracy (as is done by FITTP).
> 0 => quantize the output image so that the least bit has
the value QUANTIZE in the units of the image. This
parameter is ignored for uv data. If FORMAT is 1 or 2, the
task will use format 2 for output if necessary to avoid
clipping the image values. If FORMAT=3, the task will
integerize the image values with QUANTIZE and then write
the image in IEEE floating point. This option is usefull
when the FITS file is to be compressed (with gzip for
example) for more efficient storage or transmission. If
QUANTIZE < 1/4 of the noise in the image, then the noise in
the output image will be only a percent or 2 larger than in
the input. This is a very dangerous option; if QUANTIZE is
set too high the image is severely compromised.
************** BE CAREFUL. ****************
DOUVCOMP...> 0 => write the uv data out in a compressed format similar
to the compressed format used on disk. This can reduce the
size of the files by as much as a factor of 3, but limits
the dynamic range within a single visibility sample to a
part in 32700 or so. It also means that a single weight is
assigned to all unflagged samples in the record. This may
be undesirable in the presence of averaging of data that
are flagged differently for different Stokes, IFs, and/or
spectral channels. <= 0 => write the samples in 3
floating-point values (real, imaginary, weight) per
channel/IF/Stokes.
NPIECE.....The UV data may be broken into NPIECE segments. Writing
several smaller files may be more reliable on magnetic tape
or across networks. If pseudo-tape disk files are being
written, the output files for the additional pieces will
have 1 or 2 appended characters in their names giving the
sequence numbers.
BDROP......If NPIECE > 1 and NPIECE > BDROP > 0, do not write the
first BDROP pieces. This option is used for those times in
which the first BDROP pieces were written to tape
correctly, but the BDROP+1 piece failed for some reason
such as running off the end of the tape.
CATNO......Range of catalog numbers over which the operation is to
take place. CATNO(1) <= 0 -> 1; CATNO(2) < CATNO(1) ->
very large.
EXPLAIN SECTION