[ntp:questions] Using Garmin GPS-III+ as Time source

Unruh unruh-spam at physics.ubc.ca
Sat Nov 22 19:18:11 UTC 2008

"Richard B. Gilbert" <rgilbert88 at comcast.net> writes:

>George R. Kasica wrote:
>> Hello:
>> Just curious if this is usable as an NTP time source.
>> I have an old Garmin GPS-III+ lying around here (its a small handheld
>> GPS unit) that I can power from an AC Adapter and get a solid GPS
>> signal out of indoors actually that will provide NEMA 0183 version 2.0
>> output from RS232 that I have already got a cable for.
>> How/can I configure ntpd to utilize this setup in linux?? Or am I
>> after something that I can't do with this unit? Does someone have an
>> alternative recommendation??
>> Thanks,

>Your Garmin GPS-III+ would seem to be designed  for navigation rather 
>than timing.

>You can probably use it but it is far from being the best tool for the 
>job.  Garmin offers the GPS18-LVC which IS designed for timing.  I 
>believe that it sells for less than $100 US.

Depends on what he needs. A simple GPS is good for say 20ms accuracy.(with
the appropriate fudge to correct the timefor the RS232 signal delay) If you
want microsecond accuracy then use the GPS18LVC which has a PPS output, But
it requires that you be handy with a soldering iron. 

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