Re: GPS 1 pulse-per-second signal

On Sep 24, 2:51 pm, Richard Henry <pomer...@xxxxxxxxxxx> wrote:
Mnay GPS receivers have a 1 PPS output which is supposedly
synchronized to UTC, given enough good satellite signlas. However,
the pulse shape and timing seems to vary from one device to another.
Does anyone have any advice on how to use this signal for
synchronizing the operation of two or more objects spread over the
Earth's surface?

Thanks for the responses and links.

What I have learned so far from this thread, the links referred to,
and a little studying on my own (please correct any errors I make
here):

There is an instant every second where UTC time transitions from one
second to the next. The point of 1 PPS signal is to allow determining
that exact instant so that devices placed remotely from each other can
synchronize their operation without direct contact. An example use of
such a system would be synchronizing a radio transmitter with a
receiver.

If a device knows its exact postion on the earth it only needs a good
signal from one satellite to determine the second transition instant.
If the device does not know its position, or knows that it is moving,
it needs data from 4 satellites to determine the position and thus the
accurate timing.

Even though there is an indicator of the exact instant in the
satellite's transmitted data, the signal cannot simply be received,
decoded and used as is. The receiver must account for the estimated
rf space and atmospheric propogation delays, a local estimate of
antenna and cabling delays, snd some electronic circuitry delay. It
can then adjust the received signal back to UTC second transition
time, and compare that calculation to an estimate derived from an
internal clock, adjusting the internal estimate accordingly.
Hopefully the internal estimate will be good enough that the
adjustment will never be more than one cycle of the reference clock.
The estimate is what is used to generate the 1 PPS UTC-synch
ronized pulse.



.

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