On 4/20/06, Roy Williams <roy-at-cacr.caltech.edu> wrote:
> Who is writing VOTables with sexagesimal in them?
Well, the USNO-B1 service from Flagstaff adds another twist and writes the
RA/DEC as a 3x1 array of doubles (e.g. "12 34 56.7") and not with the
traditional
colon-delimiters. I can't find another example quickly just now, but
I know I've
seen sexigesimal in other data sets. Note the registry validation
level is 2 and
the ConeSearch validator only issues a warning that the 'units' should
be in degrees
(they're listed as 'hh mm ss", is/would that be different than "hh:mm:ss"?).
> Surely the best thing is to convert to decimal as soon as possible, and convert back to
> sexagesimal (if wanted) at the last possible moment before the human
> eyes see it.
I agree, but ....
> Suppose I want to represent a number like 3.666667 as "3
> 2/3" or "three and two thirds"?
I take your point, but IEEE already set a standard for how to
represent a double
precision value that computers understand. The characters '3', ".',
'6', .... are just
one form of human readable representation of that, and I'd argue less
familiar to
astronomers who're mentally converting to hms/dms anyway. I'm not saying we
need to add more semantics for numbers like this, I just don't
completely buy that
"3.66667" is any more legitimate than "3:40:00.0", or "0:14:40.0" if
its an RA 8-)
In the end isn't this a service/registry compliance issue? If the
VOTable spec
says POS_EQ_RA_MAIN should be in degrees perhaps we just need to clarify
"decimal degrees" and then software is free to punt when it sees something else,
or be clever and try to parse it. BTW, I didn't mean to pick on USNO
but Mark has
a point that this is an issue.
-Mike Received on 2006-04-20Z19:46:36