[fitsbits] TDIMn

[William Pence]

In response to questions about the extent to which the FITS BINTABLE 
conventions (defined in Appendix B of the NOST FITS Standard) have been 
used, here are the cases that I'm aware of.  Please let me know of any other 
examples where these conventions have been used.

B.1 "Variable Length Array" facility
------------------------------------

This convention is supported by many FITS libraries (see 
http://fits.gsfc.nasa.gov/fits_libraries.html) and has been used for the 
past decade in a number of publicly distributed FITS data sets, including:

   - The Copernicus satellite (OAO-3) spectral data, distributed
     by the Multimission Archive at Space Telescope (MAST).

   - The standard Response Matrix calibration files (RMF) that
     are used by almost all X-ray satellite missions since the
     mid 1990s.

   - Arecibo Observatory radio telescope data.  The format of
     these data files is based on the SDFITS convention for
     interchange of single dish data in radio astronomy which
     explicitly supports the variable length array convention.

   - The IRAF data analysis software uses the variable length
     array convention when storing 'Pixel Lists' in FITS format.

In addition, the 'Tiled' image compression convention (see 
http://heasarc.gsfc.nasa.gov/docs/heasarc/fits/compress/compress_image.html) 
is layered on top of the variable length array convention and is currently 
used by several groups, including:

   - Mosaic CCD camera data taken at the Canada-France-Hawaii
     Telescope (CFHT) and publicly distributed by the CADC.

   - The CCD image archive taken for the Optical Gravitational
     Lensing Experiment (OGLE) using the 1.3m Warsaw telescope
     at Las Campanas Observatory, Chile.


B.2  The TDIMn keyword convention
---------------------------------

This convention is widely supported by many software packages and is used in 
many FITS data sets, too numerous to mention individually.


B.3  The "Substing Array" convention
------------------------------------

I'm not aware of any software packages or any FITS data files that support 
or use the full form of this proposed convention, as in these examples:

TFORMn = '30A:SSTR10'      / fixed length 10-char substrings
TFORMn = '30A:SSTR10/032'  / variable-length substrings

The CFITSIO library does support the simpler convention for specifying 
fixed-length substrings, e.g.,

TFORMn = '30A10'

however I don't know of any FITS files that have actually used this convention.


-Bill Pence
-- 
____________________________________________________________________
Dr. William Pence                          William.D.Pence at nasa.gov
NASA/GSFC Code 662         HEASARC         +1-301-286-4599 (voice)
Greenbelt MD 20771                         +1-301-286-1684 (fax)