seaman at noao.edu
Sat Sep 16 13:36:34 PDT 2006
> it takes hundreds of lines of code to understand something like 5h:
> 23m,35d:12m:23".23 and all its tortured friends.
Well, yeah, but I don't see how your proposal is going to avoid the
need for for translators when importing non-IVOA data.
> My suggestion is to say that the IVOA understands a sexagesimal
> position if and only if it fits the definition as "six numbers
> separated by non-numbers". It is a very simple defintion and yet
> accepts almost all the formats that are used.
Surely what you're describing are two sexagesimal numbers?
> an IVOA sexagesimal position must consist of the numbers RAh, RAm,
> RAs, Decd, Decm, Decs, and there can be arbitrary "non-number"
> characters separating them.
Well, there's nothing about sexagesimal formats that implies the
specification of equatorial - or even spherical - coordinates, just
base-60. Other than that, for reading a pair of coordinates, your
heuristic is serviceable.
For writing sexigesimal numbers, there's no reason not to be more
specific - IVOA can require colon separators and zero-filled, two
digit fields. (Omit leading zeros.) The final field of any
specification can be a floating point of whatever precision. Not all
sexigesimal values have three fields, many have two fields,
hh:mm.mmm, for instance. In IRAF, such a number is recognized as
simply another floating point format.
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