Re: file naming

[Chris Albertson <chrisalbertson90278@yahoo.com>]

Basically I agree except for one point.
I'd like to see the files names remain unique even if they
are in the same directory.  The reason is that files get FTP'd
into places like /incoming and if two have the same name
one gets over written.  Same if you have directoes based
on dates.  You can't combine files into one common directory
later.

Simple sequence number or OK with me, count in base
36 if you want.  Just as long as there are unique.
If you need to know something about a file the filename
is a poor place to encode information.  Read the headers.


aah@nofs.navy.mil wrote:
> 
> Tom recently suggested that I take an active part
> in any file naming discussion, since I wrote a TN
> on the process a while back.  That technical note
> was concerning the Mark III data, a much more limited
> project.
>   My feelings towards the Mark IV have already been
> stated:
>   (a) files stored on CDROM should be in an 8x3 format
>       so that they obey the ISO 9660 standard.
>   (b) if you need more characters than that to uniquely
>       identify the data, then you should use a directory
>       structure on the CDROM.
> 
> I've never been a great fan of including the 'time' as part
> of a file name; the number of characters necessary to obtain
> a unique name depends on the exposure length.  I have always
> been a great fan of a sequence number, so that automated
> processing tasks can easily access the files.
>   The ways most professional observatories name files
> usually falls into two categories:
>   (1) a filename based on the name of the observed field,
>       such as ngc4449.fit.  This can get long if you
>       start including filters, sequence numbers, on/off sky, etc.
>   (2) a filename based on the UT date plus a sequence
>       number.  Examples are y01d138.005, 990504.101,
>       j1520f233.fit (where the last one is based on the
>       last 4 digits of the Julian Date plus a 3-digit file number).
> 
> So if I were to state a preference at this stage, I would
> suggest the following:
>   (1) use a directory structure on the disk, where the
>       upper level directory indicates the site.  How the
>       site is to be named is TBD; perhaps by the system
>       'name' like TOM, MIKE, etc.
>   (2) under the site directory, use a unique filename with
>       a sequential file number.  I would suggest
>          jddddxsss.fit
>          j  -- indicates following digits are Julian Date
>          dddd - last 4 digits Julian date (9999 days is longer than
>                these systems will run)
>          x  -- single character of filter name (bvri)
>          sss - 3 digits sequence number, starting at 000
>            (1000 files should be plenty for a Mark IV)
> 
> My personal data is stored in a similar manner, though the
> file names look more like
>     yymmddfx.sss
>      yy - (year - 2000)
>      mm - month
>      dd - day
>      f  - filter name
>      x  - processing step (r=raw, d=darksub f=darksub&flatfield)
>      sss - sequence number
> but I understand that this does not uniquely identify the files
> as 'fits' and some processing programs can't handle it.  I prefer
> my format since I think in yymmdd instead of jdddd.
> Arne

-- 

--
   Chris Albertson             
   chrisalbertson90278@yahoo.com
   Redondo Beach, California
   home: 310-376-1029
   cell: 310-990-7550