Reads a FITS tape composed of simple, group or table files
The programme reads a simple or a random-groups-format FITS file (Wells et al. 1981; Greisen & Harten 1981), and writes the data into an NDF , and the headers into the NDF’s FITS extension. Table-format files (Grosbøl et al. 1988) are read, and the application creates two files: a text formatted table/catalogue and a FACTS description file (as used by SCAR) based upon the FITS header cards. Composite FITS files can be processed. You may specify a list of files, including wildcards. A record of the FITS headers, and group parameters (for a group-format file) can be stored in a text file.
There is an option to run in automatic mode, where the names of output NDF data structures are generated automatically, and you can decide whether or not format conversion is to be applied to all files (rather than being prompted for each). This is very useful if there is a large number of files to be processed. Even if you want unique file names, format-conversion prompting may be switched off globally.
TRUE
if automatic
mode is required, where the name of each output NDF structure or table file is
to be generated by the application, and therefore not prompted; and a global
format-conversion switch may be set. In manual mode the FITS header is reported, but
not in automatic.
For simple or group format FITS objects in automatic mode the application
generates a filename beginning with a defined prefix followed by the
number of the file on tape. For example, if the prefix was "XRAY"
and the
25th
file of the tape was being processed, the filename of the NDF would be XRAY25.
For table-format FITS objects in the automatic mode the application
generates a filename beginning with a defined prefix followed by the
number of the file on tape. For example, if the prefix was "cat"
and the
9th file
of the tape was being processed, the filename of the table and its associated FACTS
description file would be cat9.dat
and dscfcat9.dat
respectively. [FALSE]
!
) means that no description file will be
created, so this is now the recommended usage. If your FITS file comprises
just tables, you should consider other tools such as the Cursa package, which
has facilities for examining and processing ASCII and binary tables in FITS
files.
A suggested filename for the description file is reported immediately prior to
prompting in manual mode. It is the name of the catalogue, as written in the FITS
header, with a "dscf"
prefix.
"FITS-IRAF"
–- This uses keywords CRVALi CRPIXi, CDi_j, and is the system commonly
used by IRAF. It is described in the document “World Coordinate Systems Representations
Within the FITS Format” by R.J. Hanisch and D.G. Wells, 1988, available by ftp from
fits.cv.nrao.edu /fits/documents/wcs/wcs88.ps.Z
.
"FITS-WCS"
–- This is the FITS standard WCS encoding scheme described in the paper
“Representation of celestial coordinates in FITS”
(http://www.cv.nrao.edu/fits/documents/wcs/wcs.html
).
It is very similar to FITS-IRAF but supports a wider range of projections and co-ordinate systems.
"FITS-PC"
–- This uses keywords CRVALi, CDELTi, CRPIXi, PCiiijjj, etc, as in a
previous (now superceded) draft of the above FITS world co-ordinate system paper by
E.W. Greisen and M. Calabretta.
"FITS-AIPS"
–- This uses conventions described in the document “Non-linear Coordinate
Systems in AIPS” by Eric W. Greisen (revised 9th September, 1994), available by ftp
from fits.cv.nrao.edu /fits/documents/wcs/aips27.ps.Z
. It is currently employed by the
AIPS data analysis facility, so its use will facilitate data exchange with AIPS.
This encoding uses CROTAi and CDELTi keywords to describe axis rotation and
scaling.
"DSS"
–- This is the system used by the Digital Sky Survey, and uses keywords AMDXn,
AMDYn, PLTRAH, etc.
"Native"
–- This is the native system used by the AST library (see SUN/210), and
provides a loss-free method for transferring WCS information between AST-based
application. It allows more complicated WCS information to be stored and retrieved than
any of the other encodings.
A comma-separated list of up to six values may be supplied, in which case the value actually used is in the first in the list for which corresponding keywords can be found in the FITS header.
A FITS header may contain keywords from more than one of these encodings, in which case
it is possible for the encodings to be inconsistent with each other. This may happen
for instance if an application modifies the keyword associated with one encoding but
fails to make equivalent modifications to the others. If a null parameter value (!
) is
supplied for ENCODINGS, then an attempt is made to determine the most reliable encoding
to use as follows. If both native and non-native encodings are available, then the
first non-native encoding to be found which is inconsistent with the native
encoding is used. If all encodings are consistent, then the native encoding
is used (if present). [!]
[4,6-9,12,14-16]
will read files 4,6,7,8,9,12,14,15,16. (Note that the
brackets are required to distinguish this array of characters from a single
string including commas. The brackets are unnecessary when there only one item.)
For efficiency reasons it is sensible to give the file numbers in ascending
order.
If you wish to extract all the files enter the wildcard
∗
.
5-∗
will read from 5 to the last file. The processing will continue until the end of the
tape is reached; no error will result from this.
FALSE
, the HDS type of the
data array in the NDF will be the equivalent of the FITS data format on tape (e.g.
BITPIX=16
creates a _WORD array). If TRUE
, the data array in the current file, or all
files in automatic mode, will be converted from the FITS data type on tape
to _REAL in the NDF. The conversion applies the values of the FITS keywords
BSCALE and BZERO to the tape data to generate the ‘true’ data values. If BSCALE
and BZERO are not given in the FITS header, they are taken to be 1.0 and 0.0
respectively. The suggested default is TRUE
. FALSE
, a
format-conversion query occurs for each FITS file. If TRUE
, the value of FMTCNV is
obtained before any file numbers and will apply to all data arrays. It is ignored in
automatic mode–-in effect it becomes TRUE
. [FALSE]
TRUE
if the tape has labelled files. Labelled files are non-standard.
If TRUE
, the application skips three file marks per file, rather that one.
[FALSE]
!
) means that no log file is
produced. [!]
!
) is given no NDF will be created. This offers an opportunity to review the
descriptors before deciding whether or not the data are to be extracted. TRUE
, the
tape drive is rewound before the reading of the FITS files commences. If it is
FALSE
, the tape is not rewound, and the current tape position is read from
file USRDEVDATASET.sdf
. Note that file numbers are absolute and not relative.
REWIND=FALSE
is useful if you need to read a series of files, process them,
then read some more, without having to remember the tape’s position or apply
unnecessary wear to the tape. [TRUE]
"dscf"
prefix, or if there is no description file or if the description file does
not have the "dscf"
prefix, the suggested name reverts to the catalogue name
in the FITS header. /dev/rmt/1n
. The output NDF names will be ccd2, ccd3, ccd4, and ccd9 (assuming there
are no groups). The data will not have format conversion. TAPE
. The output files
begin with a prefix "ccd"
. Integer data arrays are converted to real using the
scale and zero found in the FITS header. A record of the headers and the names
of the output files are written to the text file jkt.log
. Wells, D.C., Greisen, E.W. & Harten, R.H. 1981, Astron. Astrophys. Suppl. Ser. 44, 363.
Greisen, E.W. & Harten, R.H. 1981, Astron. Astrophys. Suppl. Ser. 44, 371.
Grosbøl, P., Harten, R.H., Greisen, E.W & Wells, D.C. 1988 Astron. Astrophys. Suppl. Ser. 73, 359.
Harten, R.H., Grosbøl, P., Greisen, E.W & Wells, D.C. 1988 Astron. Astrophys. Suppl. Ser. 73, 365.
The application processes tapes blocked at other than an integer multiple of 2880 bytes up to a maximum of 63360, provided it is a multiple of the number of bytes per data value.
For simple or group format FITS:
IEEE floating point is supported.
If BUNIT is present its value will appear as the NDF’s UNITS component.
If OBJECT is present its value will appear as the NDF’s TITLE component.
If the BLANK item is present in the header, undefined pixels are converted from the BLANK value to Starlink-standard bad value during data conversion.
An AXIS component will be stored in the NDF if the CRVALn keyword is present. (n is the number of the dimension.) If the CRPIXn keyword is absent it defaults to 1, and likewise for the CDELTn keyword. The value of CTYPEn is made the label of the axis structure.
For groups format, a new NDF is created for each data array. The name of the
NDF of the second and subsequent data arrays is generated by the application
as the <filename>G<number>
, where <filename>
is the name of the first NDF,
supplied by you or generated automatically, and <number>
is the number of the
group.
Each group NDF contains the full header in the FITS extension, appended by the set of group parameters. The group parameters are evaluated using their scales and offsets, and made to look like FITS cards, whose keywords are derived from the values of PTYPEm in the main header. (m is the number of the group parameter.) The same format is used in the log file.
If there is no data array on tape, i.e. the FITS file comprises header cards only, then a dummy vector data array of dimension two is created to make the output a valid NDF. This data array is undefined.