Poul-Henning Kamp wrote:
In message <[email protected]>, Rob
Seaman writes:
Consider the iconic issue of timekeeping for trains, one of the
primary drivers for our current standard time zone system. Trains
clearly need to be synchronized with external clocks. Trains clearly
have some mechanism or set of procedures (imperfect or not) for doing
so. So they don't match the question asked.
Modern trains run at speeds of roughly 100 m/s. They care very much
about seconds and fractions thereof.
In fact, they run so fast that a special version of the GSM mobile
standard called "GSM-R", has been created for train-control
applications.
The main difference between plain GSM and GSM-R is that the latter
allows for dopplershift up to 140 m/s, but now railway people have
started bitching about that not being enough margin.
If you want to know what non-antique rail-road control looks like,
search for and study "ERTMS".
Very informative! (Not a hint of irony. Thanks for the info.)
However, it still doesn't address the question as asked.
James Cloos wrote:
Anything which uses a remote system to sync its time is good; leap
second announcements are part of getting a time sync.
Anything which does not require <=1 sec time-of-day accuracy is also
good. They simply do not care.
So what is left?
You may disagree with his premises, but the request was for candidates
for completely standalone systems requiring high precision clocks.
Surely the (very interesting) planes, trains, shipping, power and
military applications you mentioned fail to satisfy the first premise,
whether or not they meet the second premise.
The closest I've come up with is a self-orienting telescope system
I've heard off that can (in theory, at least) be deployed by
parachute. I'm pretty sure it uses GPS, though.
Rob
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