Avoid Delta and Atlanta

On Sun, 13 Aug 2006 22:49:05 +0200, Mxsmanic
wrote:

Jim Ley writes:

Interesting claim you're making, and one which has little basis in
fact, it will of course depend on what technology your mobile phone is
operating on, as certain formats rely on very accurate clocks and send
the exact time to the phone, they're likely a lot more accurate than
your watch.

My watch is accurate to 1 second in three million years. No cellphone
does better than that.

How do you update it for leap-seconds?

In fact, I wasn't aware of any cellphones that do anything to keep
accurate time. Which ones have such a feature?

It's not a function of the phone, it's a function of the network -
anything that is CDMA based or the majority of the 3G methods (AIUI)
have clocks synchronised with the base-station, which are GPS sync'd.

Jim.

On Sun, 13 Aug 2006 22:52:04 +0200, Mxsmanic
wrote:

mrtravel writes:

A lot of them are time synced. My phone changes timezones when turned on
after arriving in a new timezone.

To what source are they synced?

GPS Atomic clocks

Jim.

On Sun, 13 Aug 2006 03:29:20 GMT, mrtravel
wrote:

Carole Allen wrote:

On Sat, 12 Aug 2006 08:47:32 +0100, "JohnT"
wrote:

I hate to have to admit this, but I have a Junghans watch which synchronises
with the MSF transmitter (it is 10 years old). And I have both a computer
and a PDA. At which point the comparison with Mixi is at an end. Rumour hath
it that he is finding Paris too hot in the Summer and is thinking of
relocating to Seattle.

JohnT


Dear Mixi: it rains here 390 days each year.

Isn't it true that the average rainfall in Seattle is less than that of
some other major US cities?

London also has low levels of rainfall. That doesn't stop it from
being wet much of the time.
--
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DFM - http://www.deepfriedmars.com
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Mxsmanic wrote:
Miguel Cruz writes:
In some places (e.g., USA) the time on the phone is set by the
network and I must assume that's very precise.

It depends on the network; they don't necessarily set their clocks
carefully, although the smart ones do.

I don't think the service would work without accurate clocks; extremely
accurate timekeeping is a key element of the system used to select cells
and hand off calls.

It always agrees with the time on my computer, which is a good sign.

You can use NTP to keep your computer within milliseconds of the
correct time. This is built in to recent versions of Windows,
although I can't remember if it is enabled by default (and it only
synchronizes once a week by default, which can leave your PC several
minutes off).

Yes, I have used NTP to keep my computer's clock accurate for at least
10 years. Which is why its agreement with my cell phone is so
confidence-inspiring for me.

It's nice to hear, by the way, that Windows has finally caught up in
this regard.

Elsewhere I have to set it myself and I find that it loses a minute
or two a week, which is fine for my purposes. Do you require more
precision than that?

Yes. I want it to be perpetually correct within a fraction of a
second. It's easy to find watches like this today, and they are
inexpensive.

You may want that, but I don't see why it's important or why 99.99% of
people would care.

miguel
--
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Latest photos: Malaysia; Thailand; Singapore; Spain; Morocco
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On Sun, 13 Aug 2006 22:49:05 +0200, Mxsmanic
wrote:

Jim Ley writes:

Interesting claim you're making, and one which has little basis in
fact, it will of course depend on what technology your mobile phone is
operating on, as certain formats rely on very accurate clocks and send
the exact time to the phone, they're likely a lot more accurate than
your watch.

My watch is accurate to 1 second in three million years. No cellphone
does better than that.

What do you care if it's only 1 second in every year?
--
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DFM - http://www.deepfriedmars.com
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--

On Sun, 13 Aug 2006 21:16:15 GMT, (Jim Ley) wrote:

On Sun, 13 Aug 2006 22:51:39 +0200, Mxsmanic
wrote:

Yes. I want it to be perpetually correct within a fraction of a
second.

Why? For what purpose?

You never know when you might need that extra millisecond in the next
60 years.
--
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DFM - http://www.deepfriedmars.com
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--

Jim Ley writes:

How does a chain make you remember to transfer it between clothes, or
remember to have it with you?

When you put the clothing on, it's there. When you take it off, you
can feel it dangling around. Pocket watches are heavier than
wris****ches.

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JohnT writes:

You would only be able to verify that claim if you measured the time errors
over 3 million years. Not even you could do that.

You can measure the error over one day and extrapolate.

One second in three million years is an accuracy of
99.999999999998943708%, incidentally.

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Jim Ley writes:

How do you update it for leap-seconds?

The radio signals to which it synchronizes cover leap years, leap
seconds, and daylight saving time. No manual adjustment is ever
necessary.

It's not a function of the phone, it's a function of the network -
anything that is CDMA based or the majority of the 3G methods (AIUI)
have clocks synchronised with the base-station, which are GPS sync'd.

Which _can_ be GPS synchronized.

GSM (the standard used everywhere else in the world) provides for time
synchronization, also, but most GSM phones don't use it, and I don't
even know if operators keep their time signals accurate.

NTP is extraordinarily accurate for computers, if you have high-speed
Internet access. It is about 20 times more accurate for short periods
than radio control (with daily sync).

All of these methods are limited over long periods by the accuracy of
cesium atomic clocks--the aforementioned 1 second in three million
years. Cesium fountains will be the next major improvement
(possibly).

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Dave Frightens Me writes:

What do you care if it's only 1 second in every year?

I'd have to reset it yearly.

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