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

[Henri Pierre]

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> 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

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

Martin

On 26.03.2012 18:38, 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>>
   To: address@hidden <mailto:paparazzi-devel@nongnu.org>

   Subject: Re: [Paparazzi-devel] UTC and gps:itow in log files
   Message-ID: <address@hidden

   <mailto:20120326154532.190200@gmx.net>>

   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

   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@hiddencom>>
    > An: address@hidden <mailto:paparazzi-devel@nongnu.org>

    > 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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   End of Paparazzi-devel Digest, Vol 96, Issue 64
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