[fitsbits] reopening of Public Comment Period on the compression conventions

[William Pence]

I support the suggestion by Mark Taylor and Tom McGlynn to decouple the 
Image compression and Table compression proposals so that they can each 
be considered on their own merits.  I think it makes sense to discuss 
them simultaneously during this public comment period, but when the time 
comes, the proposals can be voted on separately.

FWIW, I strongly support incorporating the Image compression proposal 
into the FITS Standard because it is an elegant and very effective 
compression technique that has been used by many astronomical projects 
for more than 25 years.

I also support the newer Table compression proposal, because I think it 
is technically mature and it's feasibility has been demonstrated by one 
major project (FACT).  While it is true that table compression is more 
complicated than image compression, and the benefits are somewhat less 
(in terms of compression ratios), and it is possible that in the future 
we may think of further improvements to the table compression technique 
(but these will not invalidate any FITS files that conform to the 
current proposal), I don't think any of these reasons are strong enough 
grounds to not approve this proposal now.

Finally, in response to Mark's remark about the burden that supporting 
tile-compressed FITS images or tables could impose on software 
developers, I would suggest a simpler solution in this case:  Just pipe 
the compressed FITS file to an external uncompression program (funpack 
in this case) and then process the output uncompressed FITS file as 
usual.  Just as it usually is not cost effective to write one's own 
software to directly read other compressed file formats (e.g., gzip or 
bzip2) most existing FITS software does not need the capability to 
directly read compressed FITS files and instead can rely on external 
uncompression utility programs to do that job for them.

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