Re: [Paparazzi-devel] Paparazzi-devel Digest, Vol 96, Issue 64

[Martin Mueller]

Hi Henri,

the on-board software is not aware of leap seconds and uses GPS time as 
the only time source. The ground station uses 15 leap seconds.

https://github.com/paparazzi/paparazzi/blob/master/sw/lib/ocaml/latlong.ml#L474

What other time source do you have in mind?

Martin


On 29.03.2012 10:56, Henri Pierre wrote:
> Hi Martin
>
> ok thanks.
> So you mean that, in paparazzi, UTC is produced from itow and not from any
> other source ?
>
> Regards
> Henri
>
>
>
> Le 27 mars 2012 07:41, Martin Mueller <address@hidden
> <mailto:address@hidden>> a écrit :
>
>     Hi Henri,
>
>
>      > UTC is 12:57:38.020  and GPS:itow is 305873250.
>
>     ITOW is milliseconds since Sunday 0:00
>
>     305873.250 / 86400 = 3.54 (3 = Wednesday)
>
>     0.54 * 24 = 12.96 (12:xx:yy)
>
>     0.96 * 60 = 57.88 (12:57:yy)
>
>     0.88 * 60 = 53 (12:57:53)
>
>     15 leap seconds from 1980 until today
>     http://en.wikipedia.org/wiki/__Leap_second
>     <http://en.wikipedia.org/wiki/Leap_second>
>
>     53 - 15 = 38 (12:57:38.250)
>
>     the other way around (not using leap seconds)
>     
> https://github.com/paparazzi/__paparazzi/blob/master/sw/__airborne/subsystems/gps/gps___mtk.c#L92
>     
> <https://github.com/paparazzi/paparazzi/blob/master/sw/airborne/subsystems/gps/gps_mtk.c#L92>
>
>     Martin
>
>
>     On 26.03.2012 18 <tel:26.03.2012%2018>:38, Henri Pierre wrote:
>
>         Ok, thanks for your answer.
>         So, where does this information UTC comes from ?
>
>
>
>
>             Message: 2
>             Date: Mon, 26 Mar 2012 17:45:32 +0200
>             From: "Marc Schwarzbach" <address@hidden
>         <mailto:address@hidden>
>         <mailto:address@hidden <mailto:address@hidden>__>>
>             To: address@hidden
>         <mailto:address@hidden>
>         <mailto:address@hidden
>         <mailto:address@hidden>>
>
>             Subject: Re: [Paparazzi-devel] UTC and gps:itow in log files
>             Message-ID: <address@hidden
>         <mailto:address@hidden>
>         <mailto:address@hidden
>         <mailto:address@hidden>>>
>
>             Content-Type: text/plain; charset="utf-8"
>
>             Dear Henri,
>
>             thats an issue with the leap seconds reflected in UTC
>         http://en.wikipedia.org/wiki/__Coordinated_Universal_Time
>         <http://en.wikipedia.org/wiki/Coordinated_Universal_Time>
>
>             GPS overall time has started in the 80s and does not count
>         for them.
>
>             Should be a searchable issue...
>
>             Cheers
>
>             Marc
>
>
>             -------- Original-Nachricht --------
>          > Datum: Mon, 26 Mar 2012 17:36:19 +0200
>          > Von: Henri Pierre <address@hidden
>         <mailto:address@hidden>
>         <mailto:address@hidden <mailto:address@hidden>>>
>          > An: address@hidden
>         <mailto:address@hidden>
>         <mailto:address@hidden
>         <mailto:address@hidden>>
>
>          > Betreff: [Paparazzi-devel] UTC and gps:itow in log files
>
>          > Hello
>          >
>          >
>          > I've just done an export of a flight session using the log
>             plotter and I'm
>          > facing an issue while trying to match
>          > UTC and gps:itow fields. For example on a row :
>          > UTC is 12:57:38.020  and GPS:itow is 305873250.
>          >
>          > According to my calculation, this itow refers to 12:27:53.25
>               which is
>          > different from UTC in the file.
>          >
>          > Do anybody has an explanation ? what does UTC stands for ?
>          >
>          > Regards
>          > Henri
>
>             --
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>
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>             End of Paparazzi-devel Digest, Vol 96, Issue 64
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