[time-nuts] Is possible precise 1pps?

Bob Camp lists at rtty.us
Wed Mar 13 10:06:18 EDT 2013


A GPS that uses position hold gets it's coordinates from one of two possible

1) You measure the actual antenna location with a precision survey grade GPS
and enter them.


2) The GPS does a survey for some amount of time. It averages it's own
"reasonable" location estimates over this time period. With 48 hour
averaging and a good sky view the location estimate can be pretty good.

The position hold function allows the GPS to come up with a time estimate
from a small number of satellites. This is useful when the sky view is not
very good. 

A position error of one meter can translate into a time error of about 3 ns.
Most GPS engines are rated for a 3 meter error, so that would be roughly 9
or 10 ns. Since the exact error depends on the stat's location relative to
the error vector, the actual error will vary a bit (= it looks like noise).


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of hutta.j at seznam.cz
Sent: Wednesday, March 13, 2013 9:04 AM
To: time-nuts at febo.com
Subject: [time-nuts] Is possible precise 1pps?

I have GPS without  "position hold", I wonder how precise 1PPS, which I want
to use for disciplined OCXO.
You do not know how GPS with "position hold" calculates the measured 
coordinates vs know the real coordinates of the expected error timestamps 1

Thansk for information
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