sexagesimal
Rob Seaman
seaman at noao.edu
Mon Sep 18 11:56:34 PDT 2006
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
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