On Thu, Apr 23, 2015 at 7:19 AM, Julien Demaria <[email protected]> wrote:
> I’m also not an expert on this: > > “GPS, Global Positioning System time, is the atomic time scale implemented > by the atomic clocks in the GPS ground control stations and the GPS > satellites themselves. GPS time was zero at 0h 6-Jan-1980 and since it is > not perturbed by leap seconds GPS is now ahead of UTC by 16 seconds.” > It seems to me then, that the "right" way is to express this time as: time_unit since 1908-01-06T00:00:00Z since that is technically exactly correct. clients are likely to translate to year-month-day-hour-minute-second using UTC, but maybe not. And as others have pointed out, most libs don't do leap seconds anyway, so are using "GPS time" whether they specify it or not. I guess what I am saying is that this isn't really a "how to encode it in CF" question -- if you use that epoch, then it becomes entirely up to the client what time it wants to translate to. -Chris > http://www.leapsecond.com/java/gpsclock.htm > > a more detailed explanation: > > https://confluence.qps.nl/display/KBE/UTC+to+GPS+Time+Correction > > > > Thanks in advance, > > > > Julien > > > > >Jonathan Gregory j.m.gregory at reading.ac.uk > > >Thu Apr 23 07:58:09 MDT 2015 > > > > > >Dear Julien > > > > > >Could you explain what the difference is between GPS time and UTC (for a > non- > > >expert such as me)? > > > > > >Thanks > > > > > >Jonathan > > > > *De :* Julien Demaria > *Envoyé :* jeudi 23 avril 2015 14:51 > *À :* '[email protected]' > *Objet :* How to define time coordinate in GPS? > > > > Hi, > > > > I need to define a time coordinate variable which use the GPS time > referential instead of UTC, but I did not found how to specify this. > > For the moment my variable look like this : > > > > int64 time_stamp(rows) ; > > time_stamp:standard_name = "time" ; > > time_stamp:units = "microseconds since > 2000-01-01 00:00:00" ; > > time_stamp:_FillValue = -1L ; > > > > Thanks in advance, > > > > Julien > > > > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception [email protected]
_______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
