sexagesimal

[Rob Seaman]

On Sep 18, 2006, at 10:56 AM, Alberto Conti wrote:

> I believe the issue IS formats. The IVOA should recommend a  
> standard for the VO grounded in what users need/want thereby  
> "guiding" users toward a better experience  and an easier  
> integration of VO tools.

Ok.  "Angles shall be referenced in degrees.  Time-like angles, e.g.,  
right ascension or hour angle, shall otherwise be in units of hours.   
One hour equals 15 degrees at the equator.  Variables to store angles  
should be double precision for most purposes.  Units of angular (or  
temporal) quantities may be encountered in degrees, minutes or  
seconds of arc, in hours, minutes, or seconds of time, or in  
radians.  Representations of quantities in units of radians or  
seconds of either time or arc shall be decimal.  Representations of  
quantities in units of degrees or hours or of minutes of either time  
or arc may be in decimal or sexigesimal.  The only variations of  
sexagesimal notation that IVOA facilities are guaranteed to recognize  
use a colon separator with no embedded whitespace allowed.  Either  
one or two colons are permitted with each successive colon  
representing a factor of 1/60 or 1/3600, respectively.  The sign of  
the most significant base-60 field will be taken to apply to the  
entire sexigesimal quantity.  No other field may be signed.  Only the  
least significant field may contain a decimal representation - all  
other fields must be integers.  The most significant field is  
unbounded, in both positive and negative directions.  External bounds  
may be explicitly applied.  Fields other than the most significant  
are bounded between 0 (zero) and 60, open above."

Got interrupted at the end and lost my train of thought, but you get  
the idea.  When there is a text box requiring entry, give one of  
those little grayed out examples along the lines of "hh:mm:ss.ss", or  
what have you.

Rob