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Re: [gpsd-dev] Time autonomy

From: Gary E. Miller
Subject: Re: [gpsd-dev] Time autonomy
Date: Tue, 24 Feb 2015 12:41:04 -0800

Yo Eric!

On Tue, 24 Feb 2015 14:58:57 -0500 (EST)
address@hidden (Eric S. Raymond) wrote:

> This will yield nearly correct time provided either (a) you trust the
> system clock, or (b) the device is on continuously from a date during
> its build era (e.g. before the first rollover after BUILD_EPOCH), and
> gets at least one valid fix per week.  (There are optimistic scenarios
> in which fix frequency can drop to once per *era* without worrying
> edge cases.)

Not the case on a RasPi.  No battery back clock, and often a lot
of downtime.

> 6. If you had to increment saved_epoch in step 3, write it
> /var/run/gps-epoch at shutdown time.

But only if you knwo the gps-epoch to save is good.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
        address@hidden  Tel:+1(541)382-8588

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