[ntp:questions] Local time sources

Jaap Winius jwinius at umrk.nl
Wed May 12 13:32:40 UTC 2010

On Tue, 11 May 2010 15:10:50 +0000, unruh wrote:

> ... note that chrony also now (1.24 version) allows use of gpsd to
> synchronize your clock with the Garmin ( and also does not have the
> problem you mention with ntpd that if it freeruns too long, it may not
> resynchronize-- it will and do so far faster than ntpd does.)

Another interesting tidbit. I've added it to my webpage.

> It is hard to imagine that the suction cup could fail and you not notice
> it with the gps mounted where it is. ...

Well, I don't live in the hallway and so far it has always been noticed 
within a few hours. I suppose it would be possible to write a script to 
sound an alarm whenever a significant variation in the signal from the 
GPS is detected, but such measures would be of little benefit in the 
event of my absence. I think a redundant receiver is a much better way to 
tackle this problem and the dangling GPS device will be noticed soon 
enough anyway.

> ... I'm afraid my family would shoot me.

What charming family values. Sounds like a nest of hot-headed, anal 
retentive technical types. :-))

> I run the cable out a basement window and the gps is mounted on the
> front iron rails of the house using its magnetic mount. It sees about
> 1/4 of the southern sky (tall trees on the street ahead of it, house
> behind it), but that seems to be enough.

A view of the ecliptic, which includes the stationary SBAS satellites, is 
always better than a polar view.

Before it was mounted in the skylight, my GPS device had something like a 
120 degree view of the northern sky (from the Netherlands), but despite 
the fact that it requires a lock on only one satellite at all times, it 
would still lose synchronization regularly. On the other hand, a friend 
of mine, who lives nearby, still makes do with a similar view of the 
southern sky and never loses synchronization.



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