# Apple Watch oscillator and synchronization



## rationaltime (May 1, 2008)

1 JAN, 2016

There is a recently published report about the Apple Watch on board oscillator
and synchronization method as described by the Apple VP of technology. It is
interesting reading.

The same story at two sites:
Here's how Apple synchronized all your Apple Watches 

Apple's Kevin Lynch Explains Method Behind Apple Watch's Precise Timekeeping 

The Apple Watch, and the the iPhone for that matter, appear to have a limited
operating temperature range (0-35C). The watch acts as a heat sink for the 
wrist, or the other way depending on the ambient temperature.


> Apple also designed the Apple Watch to be an exquisitely accurate
> timepiece, building in what's known as a crystal temperature-control oscillator.
> Its job is to manage the vagaries of extreme temperatures, to compensate for
> drift and keep the Apple Watch time-accurate.


That seems promising, but if I wanted to get my product to market why wouldn't
I just buy a real time clock (RTC) from a vendor? A RTC draws maybe 100 µa
and cost a few $ in low quantity. Those RTC are temperature compensated.
On this forum you discuss the difference between temperature control and
temperature compensation. Though temperature control seems possible in
the Apple Watch, I wonder if perhaps that distinction was lost as the story
passed from the Apple engineers to the managers.



> ... not only is the Apple Watch extraordinarily accurate, but take
> any two Apple Watches and hold them side-by-side and you will see the
> second hands moving in perfect unison.





> There are, by his count, 15 such "Stratum One"-level Network Time Servers
> (NTP) (one level down from an atomic clock), scattered around the world.
> They're all housed in buildings with GPS antennas on the roof that talk, you
> guessed it, to GPS satellites orbiting the earth, which all get their time
> ...


Apple uses the cellular network to query a time server on the Internet?
The cellular base station knows the NTP time. However, perhaps the phone
will use "wi-fi" to bypass the cellular network. Still, the iPhone has a GPS
receiver. The phone must read the GPS time before it can determine location.
Where is it the iphone has access to the Internet but no cellular or GPS
coverage?

Of course, it is possible synchronizing the time is a cover for getting all
the Apple Watches and iphones to "phone home" for undisclosed purposes.

Perhaps the experts here have more insight than I do about all this, and
can explain it to us.

Thanks,
rationaltime


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## Tom-HK (Jan 6, 2015)

TCXOs are not uncommon in electronics. They may improve the accuracy of a device's time-keeping over a non-TC oscillator, though they tend not to be anywhere near as accurate as dedicated TC applications developed specifically for wristwatches. Here's an article about how one particular TCXO manufacturer has been looking to get into the wearables market: SiTime 32 kHz MEMS TXCO targets wearables: Interview with founder and Chief Scientist Dr. Aaron Partridge

The spec. sheet states an accuracy of 5 ppm. Now, the TXCO that the Apple watch uses might well be more accurate than this, but this sort of accuracy would not be unexpected or unusual in the wider world of electronics, even though the term 'TXCO' is the same as that used by the makers of high accuracy watch movements, such as ETA, Seiko and Citizen.

I don't know the intrinsic accuracy of the iPhone, but the Apple watch is said to be four times more accurate. Unless the iPhone is already impressively accurate (without time sync) then the inherent accuracy of the Apple watch is unlikely to be in the same ball park as a true HAQ. Given a reliable sync, however, it wouldn't need to be. The articles suggest that network latency is adjusted for in the translation of the NTP reference through to the watch's display, and while the watch may not be in constant receipt of a sync signal, it's better-than-average TCXO will help to minimise drift between syncs. The sync itself probably comes from Apple's centralised time servers during any one of the phone's regular daily connexions.


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## rationaltime (May 1, 2008)

Hi Tom,

The SiT1552 TCXO you point to is temperature compensated rather than
temperature controlled. It is much lower power than I guessed, but that 
is for standby mode. It also does not contain the RTC logic. That makes
sense. Putting the clock logic on the processor reduces the I/O count.

The SiT1552 accuracy of 5 ppm is about 13 s/month. Even with network
updates, my read is the article suggests the Apple Watch does a lot 
better than that. Of course the watch operates over a smaller temperature
range than the oscillator.

A RTC requires some logic capability. When the temperature compensation
is made an offset could be added, and we might expect to find that feature
in a RTC. That would be interesting to readers here as it provides a user
input to correct for crystal aging or calibration.

(RTC = real time clock)


Thanks,
rationaltime


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## ronalddheld (May 5, 2005)

rationaltime said:


> Hi Tom,
> 
> The SiT1552 TCXO you point to is temperature compensated rather than
> temperature controlled. It is much lower power than I guessed, but that
> ...


I supposed we are not going to learn any hardware and software details beyond what was published?
I can see this mass synchronization being used by Apple for some purpose.


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## tmathes (Jan 11, 2013)

ronalddheld said:


> I supposed we are not going to learn any hardware and software details beyond what was published?
> I can see this mass synchronization being used by Apple for some purpose.


I've dealt with Apple as a supplier. I've seen tight-lipped and arrogant to deal with but they're in a class by themselves. Their secrecy, even with their vendors, is, ahem, 'legendary'. It's part of why I want none of the products nor services from that company. I'm definitely the 'anti' iFruit fanboi.

Whatever you see published is all you'll get from the masters at One Infinite Loop. And you will be grateful they told you anything!


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## rationaltime (May 1, 2008)

I suppose that is true. We will not hear more about this from Apple.

Still, those real time clock modules are out there for pretty cheap.
You can talk to some of them with arduino or raspberry pi, which are
also pretty low price. You might even use a USB to I²C bridge to go
to a computer. Those packages are probably surface mount devices,
but they are relatively low speed. There are probably small experimenter
boards out there.

I know there was the development kit from TI, but that activity
appears to have gone quiet. Though not on the wrist you could
make a disciplined oscillator real time clock. This is another 
opportunity.


Thanks,
rationaltime


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## jisham (Oct 21, 2015)

rationaltime said:


> Still, those real time clock modules are out there for pretty cheap.
> You can talk to some of them with arduino or raspberry pi, which are
> also pretty low price. You might even use a USB to I²C bridge to go
> to a computer. Those packages are probably surface mount devices,
> ...


Adafruit has an "Ultra-Precise" RTC/TCXO for under $20 USD.

https://www.adafruit.com/products/255

It claims they measure the temperature and switch in a capacitor from a bank to maintain the frequency. Even so, they claim an accuracy of 3.5ppm or 1 minute per year (110 spy by my math). Good, but not HAQ territory.

The basic building blocks are out there, but it still takes some engineering magic to get it into HAQ levels of accuracy.


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## gangrel (Jun 25, 2015)

3.5 ppm is approximately 9 seconds per year. Roughly 500,000 *minutes* in a year; 31.5 million seconds.


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## chris01 (Jan 5, 2011)

gangrel said:


> 3.5 ppm is approximately 9 seconds per year. Roughly 500,000 *minutes* in a year; 31.5 million seconds.


Your arithmetic has gone astray:
Correct, there are 31.5 million sec per year
1 ppm = 31,500,000 / 1,000,000 = 31.5 seconds
3.5 ppm = 31.5 x 3.5 = 110.25 seconds


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## ronalddheld (May 5, 2005)

You


gangrel said:


> 3.5 ppm is approximately 9 seconds per year. Roughly 500,000 *minutes* in a year; 31.5 million seconds.


Isn't 9 s/y ~.3 ppm?


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## gangrel (Jun 25, 2015)

I'm clearly brainfried.....


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## chris01 (Jan 5, 2011)

gangrel said:


> I'm clearly brainfried.....


Who isn't, after Christmas & New Year excesses?
I think you divided 31.5M by 3.5M instead of the two steps.
Back to our normal programming ...


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## ronalddheld (May 5, 2005)

Maybe we need to understand how the Apple servers stay closer to the GPS references than other pooled servers?


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## gangrel (Jun 25, 2015)

chris01 said:


> Who isn't, after Christmas & New Year excesses?
> I think you divided 31.5M by 3.5M instead of the two steps.
> Back to our normal programming ...


Well, celebrating fog.  I like fog every now and again, and we got some...first time in AGES. So my brain, pre-caf, was definitely in a fog.
Appropriate, too; got a non-HA Fred Constant ordered, and it's stuck in a weather delay too. Just like my brain. 

We might *want* to know how Apple does it...but they'll never tell us.


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## Hans Moleman (Sep 24, 2007)

ronalddheld said:


> Maybe we need to understand how the Apple servers stay closer to the GPS references than other pooled servers?


I don't think Apple's claimed 50 milliseconds offset is spectacular.

A computer running NTP easily achieves 10 milliseconds.

Apple's marketing, and I have give them that, is spectacular.


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## wbird (Feb 25, 2015)

Apple does claim all their watches are accurate to 50ms. That is pretty incredible.

I should mention that recently the apple boards have been talking about the improved accuracy of the time on their phones. Are the two related, don't have a clue. But I can say my phone seems to always be dead on recently.


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## ronalddheld (May 5, 2005)

Hans Moleman said:


> I don't think Apple's claimed 50 milliseconds offset is spectacular.
> 
> A computer running NTP easily achieves 10 milliseconds.
> 
> Apple's marketing, and I have give them that, is spectacular.


50 ms is not that good, but that value over many watches spread over large areas is noteworthy.


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## dmmartindale (Mar 26, 2010)

rationaltime said:


> 1 JAN, 2016
> 
> That seems promising, but if I wanted to get my product to market why wouldn't
> I just buy a real time clock (RTC) from a vendor? A RTC draws maybe 100 µa
> ...


An RTC is a stand-alone oscillator that still has some error, and still drifts with respect to the correct time. If you want all Apple Watches to stay in sync (within the eye's ability to detect), you still need to synchronize all of them to an external source.

It's likely that Apple used a temperature-compensated oscillator of some sort, since temperature regulation requires much more power. However, the device has a CPU in it, so all that's needed to do temperature compensation is a crystal, a thermistor to measure temperature, and a table of crystal frequency vs. temperature. In principle, the Watch could also update its temperature compensation table over time. Every time the time is synced, the software could compare the predicted (temperature compensated) time with the correct time, and then make adjustments to the portion of the temperature compensation table that was used since the previous sync.



> Apple uses the cellular network to query a time server on the Internet?
> The cellular base station knows the NTP time. However, perhaps the phone
> will use "wi-fi" to bypass the cellular network. Still, the iPhone has a GPS
> receiver. The phone must read the GPS time before it can determine location.
> ...


Cellular base stations know the correct time at some level, in order to synchronize with the network. However, the time received by phones connected to that network is not necessarily GPS-derived, and not even necessarily correct (I've seen it be wrong).

An iPhone contains a GPS receiver, and a full GPS receiver knows the time to sub-microsecond precision. However, the GPS receiver uses a lot of power, and the iPhone seems to keep it turned off except when absolutely needed. It uses other information (e.g. visible WiFi routers) to determine location some of the time.

It sounds like Apple has built a network of time servers, the associated iPhone periodically synchronizes its own clock with one of the time servers using NTP or something very similar, and then the iPhone synchronizes the watch. That probably uses less power than turning on the GPS. Less accurate as well, but if they are only aiming for 50 ms accuracy that's not very difficult.

- Dave


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## ronalddheld (May 5, 2005)

Apple SW and HW are so propriatary, but I suspect TC with fixed tables versus dynamically determined table entries. I doubt anyone from Apple would confirm or deny this.


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## Bill R W (Nov 9, 2015)

Has anyone with an Apple Watch done any testing to see whether the watch meets the 50 ms accuracy claim? A function of both its ability to synch time accurately and the accuracy of its oscillator between synchs. As a test of point-in-time accuracy rather than drift over an interval, you might need a GPS-based clock or PPS output to do the test.


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## ronalddheld (May 5, 2005)

Bill R W said:


> Has anyone with an Apple Watch done any testing to see whether the watch meets the 50 ms accuracy claim? A function of both its ability to synch time accurately and the accuracy of its oscillator between synchs. As a test of point-in-time accuracy rather than drift over an interval, you might need a GPS-based clock or PPS output to do the test.


I was wondering if someone would turn off the radios and let it drift for enough time to see whether the Time part of the movement is TC?


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## wbird (Feb 25, 2015)

I'm pretty sure if they weren't meeting claimed accuracy, Samsung would have told us. A quick look on the Apple forums, shows people are commenting on how accurate their cell phones are now that ATT is using time.gov for time, no complaints on the watch accuracy, not one.

Considering how rare it is for me not to have signal, and Bluetooth only has to send time data to the watch to maintain accuracy, I don't think they need TC. The phone is doing all the heavy lifting. The watch doesn't even have its own gps.


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## ronalddheld (May 5, 2005)

wbird said:


> I'm pretty sure if they weren't meeting claimed accuracy, Samsung would have told us. A quick look on the Apple forums, shows people are commenting on how accurate their cell phones are now that ATT is using time.gov for time, no complaints on the watch accuracy, not one.
> 
> Considering how rare it is for me not to have signal, and Bluetooth only has to send time data to the watch to maintain accuracy, I don't think they need TC. The phone is doing all the heavy lifting. The watch doesn't even have its own gps.


I could go to my Apple store and ask, but expect no one knows details about the movement or timing network


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## wbird (Feb 25, 2015)

Ron, I doubt anyone in the store can answer your questions but if you are popping into the Apple Store you might want to just line up 4 or 5 watches and burst photo them. Heck use one of their iPhone's and just take a pic of the pics with your phone. They will all change in sync. It's pretty remarkable when you see it.

I might pop in and do it if I find some time.


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## ronalddheld (May 5, 2005)

wbird said:


> Ron, I doubt anyone in the store can answer your questions but if you are popping into the Apple Store you might want to just line up 4 or 5 watches and burst photo them. Heck use one of their iPhone's and just take a pic of the pics with your phone. They will all change in sync. It's pretty remarkable when you see it.
> 
> I might pop in and do it if I find some time.


i would appreciate it if you did as I would rather talk to them. I do notknow if there are that many watches that close together in my store.Edit: asked an Apple salesman an he had no idea.


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## wbird (Feb 25, 2015)

Having trouble loading the photos. Had a total of 6 watches in various groups all in sync the only photo I could load is this one. What is weirder is they were in demo mode, not connected to a phone, yet the time was dead on and they were in sync.


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## ronalddheld (May 5, 2005)

wbird said:


> Having trouble loading the photos. Had a total of 6 watches in various groups all in sync the only photo I could load is this one. What is weirder is they were in demo mode, not connected to a phone, yet the time was dead on and they were in sync.


They were initially synced to a phone?Another thought: without an Apple watch will the IPhone be synced within 50 ms?


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## mikahe (Nov 27, 2013)

Apple Watches have built-in Wifi ja once network(s) are set up using the paired iPhone, watch can use Wifi independently for many things. Hopefully time sync using NTP is one of them. Even better if internal PPM keeping (like nptd driftfile) is implemented for offline usage.


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## Hans Moleman (Sep 24, 2007)

mikahe said:


> Apple Watches have built-in Wifi ja once network(s) are set up using the paired iPhone, watch can use Wifi independently for many things. Hopefully time sync using NTP is one of them. Even better if internal PPM keeping (like nptd driftfile) is implemented for offline usage.


Here's how Apple synchronized all your Apple Watches


The watch needs an iPhone for the time.
The watch has a 'crystal temperature-control oscillator'. It is 4 times better than an ordinary oscillator.

Only 4 times? And I thought that TC movements could claim 10 times better.


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## ronalddheld (May 5, 2005)

Hans Moleman said:


> Here's how Apple synchronized all your Apple Watches
> 
> 
> The watch needs an iPhone for the time.
> ...


Not as good TC tables as other manufactures? The IPhone needs the Apple watch to achieve 50ms?


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## wbird (Feb 25, 2015)

I would say move this to WUS Apple forum but no one there seems to care. On the official Apple forum at Apple people were angry that their iPhones were 4X less accurate than the Apple Watch, they could care less about the watch having 50ms accuracy, why didn't they improve phone too.

Kind of makes Adams comments in the article all the more bizarre. Lynch was the project leader and is very familiar with technology and watches. When he said accuracy was important and 50ms for an Apple Watch, and it's 4X better than an iPhone hard to believe he didn't know the specs for each.

By the way the kid at the store said that these phones have been on the floor a long time, they were synced when they were first setup, put in demo mode and that's it. I asked if he was sure they weren't on wifi or Bluetooth with something and he was pretty sure they weren't.

Considering temp doesn't move all that much in the store it's not inconceivable that they are pretty good at holding time. However it's still impressive.

What got lost in this was the complaint on how inaccurate cellphone time is just went up in smoke. An iPhone apparently is accurate to +\- 0.2s. I guess that would make it about as good as an RC watch most of the time.


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## ronalddheld (May 5, 2005)

wbird said:


> I would say move this to WUS Apple forum but no one there seems to care. On the official Apple forum at Apple people were angry that their iPhones were 4X less accurate than the Apple Watch, they could care less about the watch having 50ms accuracy, why didn't they improve phone too.
> 
> Kind of makes Adams comments in the article all the more bizarre. Lynch was the project leader and is very familiar with technology and watches. When he said accuracy was important and 50ms for an Apple Watch, and it's 4X better than an iPhone hard to believe he didn't know the specs for each.
> 
> ...


How is an IPHone that intrinsically accurate? Why would the Iwatch be more accurate then the Phone?


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## dmmartindale (Mar 26, 2010)

ronalddheld said:


> Another thought: without an Apple watch will the IPhone be synced within 50 ms?


One data point: I have an old iPhone 4S, but it's running the current version of iOS (9.2.1). This morning I woke it up and started running the Emerald Time app, which gets the current time via NTP and displays the difference between that and the iPhone internal time. The phone local time error started out as 160 ms. Then, while I was watching, the phone reset its time, Emerald Time re-checked its NTP servers, and the error had dropped to 1 ms.

So it appears that iPhones now periodically sync themselves to Apple's own time servers. I've seen this happen several times recently. It sounds like the network of Apple time servers were set up for, or at least coincident with, the Apple watch introduction. In years past, the phone seems to have obtained time from the cellular network, and I have seen it have many seconds of error.

Part 2: The same iPhone, when checked 10 or 15 minutes later, was 500 ms slow. So either the local oscillator is really awful, or the process of sleeping and waking up managed to lose a significant fraction of a second. This is a 4-year-old phone, so current Apple phones may perform better.

I understood Apple's statement about the iWatch oscillator being "4 times better" than the phone oscillator as statistics about the two oscillators alone. That means that the watch will drift more slowly than the phone does between NTP syncs. But the watch could do even better if (for example) the watch uses an NTP daemon to calculate and adjust for local oscillator drift, while the phone just resets its time periodically without adjusting for drift.

- Dave


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## wbird (Feb 25, 2015)

Ron I don't know if an iPhone is all that intrinsically accurate it's just connected a lot as far as the watch don't have a clue.

Dave had some interesting data, but since the watch only works with the iPhone 5 and later that may explain the drift. Maybe the recent models are better.

A million theories on the various sites, on how Apple does it, but if I were to guess, I think the initial time that the phone receives is very accurate, and the watch just has the ability to hold the time better between updates. The phone will drift more. Who knows just a guess.

Just to add to the confusion, from past photos you see I have an iPhone 6. I received an update to the Hoptroff app which lets you do a lock to NTP time, refresh phone time, and it displays how far off the phone time is from NTP. Each time I run it, it is less than 50ms.


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## ronalddheld (May 5, 2005)

wbird said:


> Ron I don't know if an iPhone is all that intrinsically accurate it's just connected a lot as far as the watch don't have a clue.
> 
> Dave had some interesting data, but since the watch only works with the iPhone 5 and later that may explain the drift. Maybe the recent models are better.
> 
> ...


I do not see that option on the Android version, but maybe it is because I am not linked to a Hoptroff watch?


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## wbird (Feb 25, 2015)

On the iPhone app it's under hidden treasures, and requires the phone to have wifi connection. You don't have to be linked to a watch to run it.


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## ronalddheld (May 5, 2005)

wbird said:


> On the iPhone app it's under hidden treasures, and requires the phone to have wifi connection. You don't have to be linked to a watch to run it.


I do not see those fields. When I have access to WiFi I will try it out.


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## dmmartindale (Mar 26, 2010)

wbird said:


> Just to add to the confusion, from past photos you see I have an iPhone 6. I received an update to the Hoptroff app which lets you do a lock to NTP time, refresh phone time, and it displays how far off the phone time is from NTP. Each time I run it, it is less than 50ms.


That's *very* interesting. The Emerald Time app works by polling several NTP servers (using whatever Internet connection you have - it works with both WiFi and cellular data) and displays the correct time and the offset between phone and correct time. But it cannot change the phone time, and the documentation says this is because iOS does not allow apps to change the time on the phone. So maybe that restriction has been removed in recent versions of iOS, and Hoptroff has figured out how to set the phone time.

- Dave


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## Bill R W (Nov 9, 2015)

wbird said:


> Ron I don't know if an iPhone is all that intrinsically accurate it's just connected a lot as far as the watch don't have a clue.
> 
> Dave had some interesting data, but since the watch only works with the iPhone 5 and later that may explain the drift. Maybe the recent models are better.
> 
> ...


I run Emerald Time for iPad and it shows the difference between the iPad's time and Emerald Time. When I am at home or in the office with good wifi, the difference tends to be small, often single digit milliseconds and I do not recall seeing a difference, when on wifi, greater than 50 ms. I have not, however, systematically tested or recorded the differences. This morning at home it it ranged between 2 milliseconds and 10 milliseconds checking several times over an hour or so.

I am now at the airport and using a cell connection rather than wifi. Emerald Time now reports a 56 milliseconds difference between it and the iPad Air2 clock. Running the most recent version of iOS 9. Just tried again and it now shows a 5 ms difference. Tried again and shows 31 ms difference. (I see the Hoptroff app will not compute the time difference unless you have a wifi connection.)

Not it sure if this is because iOS does not synch with Apple's time servers when on a cell connection? Or if the synch for the iPad or Emerald Time or both is less accurate in a cell connection (which seems likely). The round trip time to the servers reported by Emerald Time are longer when on a cell connection than when on a wifi connection.

I loaded the Hoptroff app this morning and see the screen that reports the time difference. Do not see where it resets the iPad clock. Maybe different on an iPhone? I should try it there. If it affects the iPad or iPhone clock, I wonder if it simply causes the clock to resample the Apple time servers rather than control the clock to reset it directly.


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## ronalddheld (May 5, 2005)

Bill R W said:


> I run Emerald Time for iPad and it shows the difference between the iPad's time and Emerald Time. When I am at home or in the office with good wifi, the difference tends to be small, often single digit milliseconds and I do not recall seeing a difference, when on wifi, greater than 50 ms. I have not, however, systematically tested or recorded the differences. This morning at home it it ranged between 2 milliseconds and 10 milliseconds checking several times over an hour or so.
> 
> I am now at the airport and using a cell connection rather than wifi. Emerald Time now reports a 56 milliseconds difference between it and the iPad Air2 clock. Running the most recent version of iOS 9. Just tried again and it now shows a 5 ms difference. Tried again and shows 31 ms difference. (I see the Hoptroff app will not compute the time difference unless you have a wifi connection.)
> 
> ...


I wonder if there is a functional difference between the Hopttoff IOS and Android apps?


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## wbird (Feb 25, 2015)

Gotta say I assumed an iPhone refresh because I keep seeing numbers below 15ms. Knowing that's way better than what I should see doing random readings on an iPhone throughout the day.

Ron I would suggest checking manually if there is an update for the Android. If not, the android may still be using NTP for the phone and watch, you just don't get the option to see it. Maybe a question for Dr. H?

I am having a hard time believing my iPhone is this accurate. If it is than I have a new time reference.


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## ronalddheld (May 5, 2005)

wbird said:


> Gotta say I assumed an iPhone refresh because I keep seeing numbers below 15ms. Knowing that's way better than what I should see doing random readings on an iPhone throughout the day.
> 
> Ron I would suggest checking manually if there is an update for the Android. If not, the android may still be using NTP for the phone and watch, you just don't get the option to see it. Maybe a question for Dr. H?
> 
> I am having a hard time believing my iPhone is this accurate. If it is than I have a new time reference.


No updates for the app. When I am at a location with free WiFi i will try. I will likely email Dr. Hopttoff in the near future.


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## Bill R W (Nov 9, 2015)

Any indication whether the new Apple Watch 2 has any improvements for basic timekeeping? Better oscillator? TC? Different synching process? Use of the GPS now included in the watch to set time or monitor accuracy? 

Have not seen this discussed in the Apple Watch forum and assume people here care more about such issues.


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## ronalddheld (May 5, 2005)

Bill R W said:


> Any indication whether the new Apple Watch 2 has any improvements for basic timekeeping? Better oscillator? TC? Different synching process? Use of the GPS now included in the watch to set time or monitor accuracy?
> 
> Have not seen this discussed in the Apple Watch forum and assume people here care more about such issues.


I was going to runs some tests, when I get version 2. If someone knows who to email at Apple, I would try.
Guessing his email address and sending one to him. Maybe I will be a response?


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## Maljunulo (Aug 14, 2016)

ronalddheld said:


> They were initially synced to a phone?Another thought: without an Apple watch will the IPhone be synced within 50 ms?


When I fire up Emerald Time on my iPhone SE it frequently reports a difference in the single digits. (in milliseconds)

The clock in my iPhone 4 was horrible, frequently off a few to several seconds, so something has changed "big time".


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## ronalddheld (May 5, 2005)

Maljunulo said:


> When I fire up Emerald Time on my iPhone SE it frequently reports a difference in the single digits. (in milliseconds)
> 
> The clock in my iPhone 4 was horrible, frequently off a few to several seconds, so something has changed "big time".


IPhone time is alleged to be inferior to the AW.


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## Maljunulo (Aug 14, 2016)

ronalddheld said:


> IPhone time is alleged to be inferior to the AW.


Well, I just did it, and the NTP server offsets were 2, 3, 2, 1, and 1 millisecond.

I have no clue about the Apple watch.


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## Fer Guzman (Feb 10, 2012)

ronalddheld said:


> IPhone time is alleged to be inferior to the AW.


Kevin Lynch from apple claimed the watch is 4 times more accurate than the iPhone.


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## ronalddheld (May 5, 2005)

The series 2 watch will be thermocompensated with the same performance with access to Apple servers via IPhone. When the watch is not connected to an IPhone the GPS can maintain the accuracy as needed.


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## Fer Guzman (Feb 10, 2012)

ronalddheld said:


> The series 2 watch will be thermocompensated with the same performance with access to Apple servers via IPhone. When the watch is not connected to an IPhone the GPS can maintain the accuracy as needed.


It's TC??? I did not know that.


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## ronalddheld (May 5, 2005)

Fer Guzman said:


> It's TC??? I did not know that.


Yes and so was the series 1 according to a blog.


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## Hans Moleman (Sep 24, 2007)

I doubt this report has all the details correct but you'll get the gist of it.


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## gangrel (Jun 25, 2015)

Come to think on it, there's no reason NOT to include TC in any smart watch, that I can see. Laziness, or disinterest if you prefer, doesn't count. A regular quartz can just use a simple counter; even something complex like a calendar module can probably be done with a PGA, which is instructions (and potentially data) implemented as actual logic circuits. A TC table might be a PGA. But with a smart watch, you've got a full-scale processor that's massively more capable than a bitty lil PGA.

Of course by that argument, GPS watches certainly, and RF watches probably, should include TC. 

This might be an interesting question to pose to the designers and product managers at Samsung, LG, Motorola, Seiko, Casio, and Citizen. If one thought an honest answer would be forthcoming. I have my doubts on THAT score.


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## Bill R W (Nov 9, 2015)

ronalddheld said:


> The series 2 watch will be thermocompensated with the same performance with access to Apple servers via IPhone. When the watch is not connected to an IPhone the GPS can maintain the accuracy as needed.


If the AW 2 has a quartz oscillator with TC, is it essentially a digital HAQ with the ability to synch time either with the Apple time server network (using an iPhone and Bluetooth) or GPS satellites?

I wonder if the user can control when or how often the AW 2 synchs. I suppose it has an airplane mode that would turn off Bluetooth at least. Battery life is short, but I wonder if it would be better if you turn off various smartphone features and just use it as a watch?

Is there anything out there from Apple with more details about the AW 2 and timekeeping? I have read various reports of what Kevin Lynch said about the original AW (AW 1) and timekeeping last December. Looking back at reports of his comments, they suggest the AW 1 has a "temperature-controlled" oscillator. Assume they meant a thermocompensated oscillator.


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## Hans Moleman (Sep 24, 2007)

Bill R W said:


> If the AW 2 has a quartz oscillator with TC, is it essentially a digital HAQ with the ability to synch time either with the Apple time server network (using an iPhone and Bluetooth) or GPS satellites?
> 
> I wonder if the user can control when or how often the AW 2 synchs. I suppose it has an airplane mode that would turn off Bluetooth at least. Battery life is short, but I wonder if it would be better if you turn off various smartphone features and just use it as a watch?
> 
> Is there anything out there from Apple with more details about the AW 2 and timekeeping? I have read various reports of what Kevin Lynch said about the original AW (AW 1) and timekeeping last December. Looking back at reports of his comments, they suggest the AW 1 has a "temperature-controlled" oscillator. Assume they meant a thermocompensated oscillator.


Actually the 50 ms quote surprises me.

Something to boast about. Something for the nerds. We do technology.

To go the whole hog, I think, they won't go. Too hard. Not sexy enough.

Fighting for the last millisecond? Never.


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## AvantGardeTime (Aug 23, 2013)

TC or not I have no interest in the AW. The thing is ugly and requires daily charging. No thanks


Sent from my iPhone using Tapatalk


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## ronalddheld (May 5, 2005)

I will try one out for the good of the group. IPhone has to appear first.


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## gangrel (Jun 25, 2015)

I'd never do an AW, but I live in the other universe...that candy-crazy one. We, at least, have more brands from which to choose. Haven't even browsed around specs on any of em in a couple years, tho. 

But the newest Google phones are coming out in October, and IIRC there's some more gear too. So it might be worth looking again, shortly after that....


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## ronalddheld (May 5, 2005)

Well if you like the Pixel phones, go for it. The same for AW watches. "No one" but me would be buying one for the chronometic properties.


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## Fer Guzman (Feb 10, 2012)

When I saw the keynote for the first AW and they mentioned the accuracy I totally nerded out and one reason I bought it was because I felt it would be easier to stay accurate than needing atomic signal or satellite syncing


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## Bill R W (Nov 9, 2015)

ronalddheld said:


> Well if you like the Pixel phones, go for it. The same for AW watches. "No one" but me would be buying one for the chronometic properties.


I suspect there are others here (including me) who might be interested in the AW2 as a watch -- digital quartz, with TC and the ability to synch its time with the Apple time servers or GPS satellites. My main question, beyond timekeeping performance, is battery life. Wondering how long the AW2 can go without a charge if you turn off Bluetooth, GPS and any other notifications (I don't really want or need more notifications or connectedness) and let it function as a digital watch. You could turn on GPS or Bluetooth when you want to synch time. My Garmin watches will go for a month or two without charging if GPS and Bluetooth are off; but they are not very good timekeepers (at least to the standards of this forum) on a standalone basis. Having to take a charger along on short trips would diminish its appeal as a travel watch.


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## wbird (Feb 25, 2015)

I'm pretty certain the goal of the Apple Watch is to reduce the level of connectivity not increase it. By filtering the messages that get displayed on your wrist, you are not constantly checking your phone for notifications, texts and emails, and you are certainly not reading long messages on your watch. As far as battery life it appears to be on par with the iphone, and I have no complaints with my iPhone as a travel phone. One more charger in my knapsack is not a deal breaker. 

I'm certain it will keep great time(never saw one off time in the store), last at least 18 hours with moderate use, and continue to add features. The reason I wasn't all that impressed with the AW1 was the water resistance and display. When you chose the analog clock face as the default, it just looked like a fake watch, not enough pixels and brightness. In direct sunlight pretty unreadable. The AW2 is supposed to have more brightness, contrast and maybe more pixels. The water resistance has been improved. I have to go check one out, and see how much this has improved.


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## ronalddheld (May 5, 2005)

Bill R W said:


> I suspect there are others here (including me) who might be interested in the AW2 as a watch -- digital quartz, with TC and the ability to synch its time with the Apple time servers or GPS satellites. My main question, beyond timekeeping performance, is battery life. Wondering how long the AW2 can go without a charge if you turn off Bluetooth, GPS and any other notifications (I don't really want or need more notifications or connectedness) and let it function as a digital watch. You could turn on GPS or Bluetooth when you want to synch time. My Garmin watches will go for a month or two without charging if GPS and Bluetooth are off; but they are not very good timekeepers (at least to the standards of this forum) on a standalone basis. Having to take a charger along on short trips would diminish its appeal as a travel watch.


I will check that when I determine the level of TC at a high level. If I have to recharge in under a week, with no radios on, and the display off, the heating would alter the results. I will try to ask at the Apple store.
Edit: maybe just leave it on the chsrger instead.


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## ronalddheld (May 5, 2005)

I now have series 2 watch. After some personalizion I should run a test. Any suggestions as to details? AW plugged in and in airplane mode and use Emerald time for the base time??


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## Bill R W (Nov 9, 2015)

ronalddheld said:


> I now have series 2 watch. After some personalizion I should run a test. Any suggestions as to details? AW plugged in and in airplane mode and use Emerald time for the base time??


Congratulations on your new watch.

In my prior tests (admittedly a small sample) of time apps for iPad, Emerald Time for iPad was generally accurate to within 50 ms of the time shown by my Garmin GPS PPS output. Apart from a GPS time reference, I would expect Emerald Time is a good reference time to use.

With regular synching, I recall Kevin Lynch saying that the AW1 would stay within 50 ms of accurate time. I have not seen any discussion of the timekeeping accuracy of the AW2.

Others more knowledgeable here than me will undoubtedly know more about how to test the watch. Given Emerald Time should not drift, but has some point in time variability, my guess is that (unless the AW2 turns out to not be that intrinsically accurate) you will want to test the watch (without synching by Bluetooth or GPS) for at least a month after initially synching it, if using visual or photographic methods to test the AW2 as a standalone TC watch for drift. Assume that the battery will not last that long even with synching turned off (although it would be great if it did). So you would either need to charge it regularly or leave it on the charger. Not sure what that would do regarding temperature and the extent to which that would influence the watch's rate.

I am curious to know if the watch will synch its time to either the Apple time server network or to GPS satellites. That would be nice, especially if the watch has TC intrinsic accuracy (perhaps I should say precision) in between synchs and reasonable battery life with the smart functions off.

Looking forward to hearing more. Have been thinking about getting one too.


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## Tom-HK (Jan 6, 2015)

Ideally I would see the watch held at a constant, moderately high temperature for a month and then at a constant, moderately cool temperature for another month, with each month being independently timed on a daily basis by the most accurate method available. As long as the temperatures are within normal operating range and typical of what a watch might expect to encounter in real world conditions, then we should see whether there is any noticeable TC effect. A non-TC watch (even one of those that keeps fantastic time on the wrist or over the course of a year) should, over each period, show markedly different rates. I have read that the Apple Watch includes some sort of TCXO, but with spec described as being just '4 times' more accurate than a pre-Apple-time-server-sync-era iPhone, I would expect it to be a bog standard implementation common to the electronics world and not the sort of high-accuracy solution that we expect to see in a HAQ.


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## Bill R W (Nov 9, 2015)

Ronald -- I unintentionally duplicated post #65 when trying to edit it to change "ms" to "milliseconds." Could you delete #65 (I tried unsuccessfully) and this one? Thanks.


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## ronalddheld (May 5, 2005)

I do not have such equipment and actually would wear the watch. My idea is to sync for a day and go to airplane mode. On the charger to keep the watch from dying. Maybe a photo check a week for a month. No idea of the level of TC but a guess is in the 10 to 50 s/y range.


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## Bill R W (Nov 9, 2015)

I find that the GPS in my iPad and iPhone will run in airplane mode. So you may want to be sure that the GPS in the AW2 is not turned on by an app or the desire to synch time. I think wifi now also works in airplane mode, to allow access to airline-provided internet and entertainment. If the AW2 has wifi, you may also need to turn that off to avoid an unintentional synch while testing.


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## ronalddheld (May 5, 2005)

Bill R W said:


> I find that the GPS in my iPad and iPhone will run in airplane mode. So you may want to be sure that the GPS in the AW2 is not turned on by an app or the desire to synch time. I think wifi now also works in airplane mode, to allow access to airline-provided internet and entertainment. If the AW2 has wifi, you may also need to turn that off to avoid an unintentional synch while testing.


I thought in airplane mode BT and WiFi are off. If location services are off, the GPS receiver is too? Have not fully read the watch manual, is a busy week leading up to Turkey day.


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## ronalddheld (May 5, 2005)

Unless someone has a better thread, I will start the test Friday. Weekly images are my goal


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## dmmartindale (Mar 26, 2010)

Bill R W said:


> I find that the GPS in my iPad and iPhone will run in airplane mode. So you may want to be sure that the GPS in the AW2 is not turned on by an app or the desire to synch time. I think wifi now also works in airplane mode, to allow access to airline-provided internet and entertainment. If the AW2 has wifi, you may also need to turn that off to avoid an unintentional synch while testing.


With my iPhone 4S (admittedly an older model, running iOS 9.3.5), turning Airplane Mode ON has the effect of turning Wifi OFF. However, you can then manually turn Wifi back ON while Airplane Mode remains ON.

The GPS remains available in Airplane Mode, presumably because GPS is an entirely passive receiver (no RF transmissions).

Location Services uses both network connection data (Wifi and cellular, possibly Bluetooth) and GPS to determine location. If all of the radio transmitters are turned off by Airplane Mode, can Location Services still use received network data (cellular and Wifi base stations transmit regularly, even when they aren't talking to anyone specific) to determine location? Does it switch to using GPS? I don't know Location Services behaves under these circumstances, and I've never seen it documented anywhere.

- Dave


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## ronalddheld (May 5, 2005)

Should take a first image not Tuesday.


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## chris01 (Jan 5, 2011)

ronalddheld said:


> Should take a first image not Tuesday.


I'm posting this image for Ronald, as he's having some technical problems:


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## Hans Moleman (Sep 24, 2007)

chris01 said:


> I'm posting this image for Ronald, as he's having some technical problems:
> 
> View attachment 10049962


Now do the same for 23 Nov 2015.


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## ronalddheld (May 5, 2005)

Hans Moleman said:


> Now do the same for 23 Nov 2015.


Sorry, Hans no time machine.
I will try for an image a week for about a month. Not certain anyone can do much with so little data.


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## Tom-HK (Jan 6, 2015)

Not sure how I missed this but I found a tear-down of the Apple Watch (Video Teardown: Apple Watch Sport | Electronics360) that reveals the XO to be a SiTime SiT15XX which, by sheer coincidence, I linked to in an earlier, speculative post. Here's the spec. sheet : https://www.sitime.com/products/32-khz-oscillators


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## ronalddheld (May 5, 2005)

Tom-HK said:


> Not sure how I missed this but I found a tear-down of the Apple Watch (Video Teardown: Apple Watch Sport | Electronics360) that reveals the XO to be a SiTime SiT15XX which, by sheer coincidence, I linked to in an earlier, speculative post. Here's the spec. sheet : https://www.sitime.com/products/32-khz-oscillators


Will have to save the links and carefully look them over.


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## ronalddheld (May 5, 2005)

Tom-HK said:


> Not sure how I missed this but I found a tear-down of the Apple Watch (Video Teardown: Apple Watch Sport | Electronics360) that reveals the XO to be a SiTime SiT15XX which, by sheer coincidence, I linked to in an earlier, speculative post. Here's the spec. sheet : https://www.sitime.com/products/32-khz-oscillators


Should it be: https://www.sitime.com/products/32-khz-temperature-compensated-oscillators-tcxo. ?


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## Tom-HK (Jan 6, 2015)

Yes, my mistake, I think it should be the link you posted.

Given the wide temperature range quoted for +/- 5 ppm, I should imagine the XO could perform considerably better through normal watch temperatures.


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## chris01 (Jan 5, 2011)

Here's Ronald's second image:


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## ronalddheld (May 5, 2005)

Anyone want to predict when I see a deviation of a second?


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## Tom-HK (Jan 6, 2015)

ronalddheld said:


> Anyone want to predict when I see a deviation of a second?


I'm going to say the fifth week. What's the prize?


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## ronalddheld (May 5, 2005)

Tom-HK said:


> I'm going to say the fifth week. What's the prize?


No prize short of,perhaps,enhanced status here?


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## chris01 (Jan 5, 2011)

Image #3 from Ronald


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## chris01 (Jan 5, 2011)

Image #4 from Ronald:


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## wbird (Feb 25, 2015)

Ron I was going to suggest that you take your photo closer to the minute change and than I could see how good the time is with Verizon on your cellphone. I know AT&T is very good and you could put to bed that whole cellphone time stinks argument, but it's not really all that important. Your data along with the data on the Apple Watch forum show it to be quite an impressive time piece.


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## BarracksSi (Feb 13, 2013)

Came to see this thread after ronalddheld and rationaltime had mentioned it over in the Apple Watch subforum --



Bill R W said:


> ... Wondering how long the AW2 can go without a charge if you turn off Bluetooth, GPS and any other notifications (I don't really want or need more notifications or connectedness) and let it function as a digital watch. ... Having to take a charger along on short trips would diminish its appeal as a travel watch.


Mine ran for close to a week off the charger in Airplane Mode with minimal usage (no Workouts to fire up the LEDs for heart rate, etc). I was primarily wanting to see if it would revert to turning the radios back on after the battery ran down, so I got impatient and turned on Workout for a couple hours on the fourth day. It helped accelerate the battery drain, and the watch went into Power Reserve mode (no functions besides displaying the time only after a button press) for another day or more.

Regarding the need to recharge -- yup, the last time I was traveling for work, my AW was my primary watch, and I carried another watch in my bag in case I didn't get a chance to keep it charged. The only time it became a problem was when I took an overnight bus trip and didn't get to settle down until the following evening, which would've been about 40 hours off-charger. I discovered the magnetic puck's sole drawback -- it doesn't hold the watch strongly enough to just leave it in my lap.

For off-network accuracy, mine lost about 0.8 seconds during a twenty-something-day stint in Airplane Mode. Maybe -1 sec/month at worst, then. The first time I noticed a difference from my atomic-sync'd Citizen, which was after maybe a week, I took a rapid-fire sequence of pics with my phone, and only one frame caught the Citizen displaying one second ahead of the AW.

Before I took the AW out of Airplane Mode last week, I also preemptively switched my iPhone's Wifi and Bluetooth _off_ to force the AW to sync itself over the internet via my home Wifi network. It re-synced with Apple's time servers pretty quickly, erasing the -0.8sec deficit it had accrued. It also gained roughly half the functionality it normally enjoys with an active phone connection (Siri, Weather, and Messages: yes; Email: no; Maps: weird; third-party apps: dependent on native support).

Early this week, I went back to normal, turning on the phone's Wifi/BT and using the AW as a connected device. Within ten minutes, the AW's convenience made itself known again -- I checked the weather while choosing a jacket from my closet and answered a call while walking downstairs to the car. I've also been able to stop handling my phone so often; I don't feel any need to have it on my person all the time.

I can't say that the AW lets me _disconnect_ from the phone and the specter of constant communication. Instead, I'll say that the connection is _thinner_. I've restricted the AW's notifications to just a few sources (the only emails it tells me about are from my VIP list, for example), so I can more easily ignore all the digital noise and just hear what I want to hear. I really like it a lot.


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## ronalddheld (May 5, 2005)

At least one more photo Monday. I will try to eyeball what was requested.


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## chris01 (Jan 5, 2011)

Image #5 from Ronald


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## ronalddheld (May 5, 2005)

An eyeball check case off about .3 s. I had worse success trying to time the AW rollover versus the iPhone


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## BarracksSi (Feb 13, 2013)

ronalddheld said:


> An eyeball check case off about .3 s. I had worse success trying to time the AW rollover versus the iPhone


If your camera has a burst mode -- or even just video -- you can grab when they change over. I shot these in a burst of pics on my iPhone 5SE:


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## Bill R W (Nov 9, 2015)

ronalddheld said:


> An eyeball check case off about .3 s. I had worse success trying to time the AW rollover versus the iPhone


My wife ordered me an AW2 as a Christmas gift. Although ordered before Christmas, Apple originally said it would not arrive until January 9th. But apparently it arrived for store pickup today.

Plan to check the watch's precision when running standalone (not synching) by using 400 fps video and a GPS PPS signal. Will look at both the AW2's digital and analog faces and will try to catch the transitions to a new second. Also quite interested in battery life, both connected and not connected.

Have also been using a watch timing app for iOS called Watch Tracker recently. Will also try that with the AW2. It's probably not more accurate than using Emerald Time and the eyeball method (the app synchs its reference time to an unidentified atomic-based internet time server (or servers?), but requires user input (tapping the screen) when the watch being tested reaches a specified time). Not free either (although only $5). I have been using it to time my mechanical watches, where a couple of tenths of a second user input error is not that important. If using Watch Tracker for a HAQ, may need a longer testing period to get a useful result (so that user input error is less important). Of course, user input error may also wash out a bit, as you use the same process to set an initial baseline. The app allows testing over multiple points in time and will save tests in multiple runs if you want. Has some graphics and does calculations for you.

Looking forward to having the AW2 in hand.


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## Bill R W (Nov 9, 2015)

Should also say that I first noticed Watch Tracker in BarracksSi's posts in the "time change" thread in the Apple Watch forum.


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## ronalddheld (May 5, 2005)

BarracksSi said:


> If your camera has a burst mode -- or even just video -- you can grab when they change over. I shot these in a burst of pics on my iPhone 5SE:


I will look to see if I Can enable burst mode or video. 
One more image and then Bill should have his watchl to use better equipment on. Two at the most, so I can actually wear the watch.


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## wbird (Feb 25, 2015)

Ron you have an iphone. Just hold the shutter button down while you're in picture mode, that's burst mode. Betting you have a computer, just hold your watch in front of the screen with time.gov or time.is and count the frames difference with each photograph in the burst. An iphone takes 10 shots per second so you have .1s resolution. If you want more detail you can look at the thread I posted on burst photography. You have the tools you need good luck.


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## BarracksSi (Feb 13, 2013)

I think burst mode on iPhones comes on the 5S and newer. My wife's 5C does a slower sequential shooting thing, but it's not a rapid "k-ssssss" of shots like my 5SE does. Her 5C also gets a bunch of individual photos while mine groups each burst into one selectable group.

Just hold down the button and it'll shoot a burst sequence. Easy-peasy.


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## wbird (Feb 25, 2015)

Not to get to off track but I agree with you a 100% BarracksSi, Apple phone camera is the goods for burst photography. If you want a pain my wife rolls in the Samsung world it bursts at around 7 to 8 frames per second,(when the phone is not bursting into flames) not very elegant for timing anything. I should mention Ron the burst photos go into a separate file called bursts in your photo library.


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## ronalddheld (May 5, 2005)

I am using the iPhone for Emerald time. the Nexus 6 is the camera as it is not connected to any network. My standalone camera is ~10 years old and may not work.


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## Bill R W (Nov 9, 2015)

Got my AW2 last night. Trying to figure it out. 

The manual does not seem to say anything about the AW2 synching its time with Apple time servers or GPS satellites. Have seen reports of what Kevin Lynch said about the AW1 and timekeeping about a year ago. I would love to know how often the AW2 synchs with the Apple time servers (when available over the internet through a Bluetooth or wifi connection), whether a user can trigger a time synch over the internet, whether the watch will synch its time with GPS satellites (or merely uses GPS to determine position without synching the watch's time function), and whether a user can trigger a GPS time synch. I would also be interested to know at least in general how the AW2 movement works when not synching and how precise Apple thinks the movement is when not synching. 

I did some comparisons today between the AW2 and a GPS PPS signal (both Garmin 18x LVC and LeoNTP) and Emerald Time for iPhone. Have not put the watch in airplane mode yet. Was curious to see how accurate the AW2 synching is and to see how various video methods would work for doing testing the AW2. Not a measurement of drift yet. 

The watch's analog faces did not work well for testing with video. I tried the analog Utility face. Was hard to see the second hand and it moves continuously, so it was also hard to precisely identify the start of a new second on the watch. (Of course, an analog face might work just fine in a test of drift over a longer period.) 

There seems to be only one general digital face that shows seconds -- Activity Digital -- so I used that. 

I tried 400 fps video with the digital face and GPS PPS. Was hard to read. May need to try in better light. One measurement seemed to show the watch 29 frames slower than the PPS signal, or about 74 milliseconds. Will have to do some more testing to see if I can get better 400 fps video. 

Switched to 60 fps video, which is higher quality and easier to read. Resolution generally lower at 16.7 milliseconds (1,000/60). Shot a 9-second sequence and could identify the start of 8 new seconds by GPS PPS. 

For 3 of the new seconds, the AW2 was one frame faster than the PPS signal -- i.e., I could see the new second starting to display on the watch in the frame one before the frame in which I could see the GPS PPS LED light up. In these cases, Emerald Time was 3 frames slow for comparison. 

For 4 of the new seconds, the AW2 showed (or started to show) the new second in the same frame that the GPS PPS LED lit up. In these cases, Emerald Time was 2 frames slow for comparison. 

In 1 of the new seconds, the AW2 showed the new second one frame slower than the GPS PPS signal. Interestingly, this was in the middle of the cases mentioned in the prior paragraph. In this case, Emerald Time was 3 frames slow for comparison. 

So the AW2 seems to have been within roughly +\- 17 milliseconds of the GPS PPS signal (a signal that should be accurate to a millisecond or better). 

The 9-second sequence was shot after the possible 74 milliseconds difference described earlier. Perhaps that earlier "measurement" was in error? Had the AW2 synched between that measurement and this sequence? Is it possible that the AW2 could have synched during the 9-second sequence? Not sure. 

Emerald Time's performance was 34-50 milliseconds off the GPS PPS signal, similar to what I have generally seen when doing some tests of Emerald Time in the past. 

Will do more testing. Interesting. 

Enjoying wearing the AW2.


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## Bill R W (Nov 9, 2015)

Perhaps I should say the AW2 was within +\- 34 milliseconds of the GPS PPS signal. Events in two different adjacent frames could potentially be the length of two frames apart (although they could be also be less far apart).


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## BarracksSi (Feb 13, 2013)

Bill R W said:


> I would love to know how often the AW2 synchs with the Apple time servers (when available over the internet through a Bluetooth or wifi connection), whether a user can trigger a time synch over the internet, whether the watch will synch its time with GPS satellites (or merely uses GPS to determine position without synching the watch's time function), and whether a user can trigger a GPS time synch. I would also be interested to know at least in general how the AW2 movement works when not synching and how precise Apple thinks the movement is when not synching.


I know that...

(1) Within a minute or two of taking my AW0 out of Airplane Mode, it had re-synced itself with Apple's servers; 
(2) There's no toggle to sync the AW by the user's command. I think it just happens periodically;
(3) I don't know about the AW syncing with GPS as mine is the first-gen version;
(4) Ditto to #3. 
(5?) Mine ran no worse than -1sec/month, maybe more like -0.8sec. It was pretty consistent in my Watch Tracker app's graph, although I also didn't wear it very often. I have no idea what Apple's specs are, and probably don't know any more than you overall because we've both read Lynch's commentary about it.


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## ronalddheld (May 5, 2005)

Apple is a highly secretive company. The details we seek are not going to be released.
The watch can sync with GPS in standalone mode. I believe the Apple server is checked 4 times a day.
Unless someone objects I will do a final image and or movie then leave things to Bill.


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## Bill R W (Nov 9, 2015)

ronalddheld said:


> Apple is a highly secretive company. The details we seek are not going to be released.
> The watch can sync with GPS in standalone mode. I believe the Apple server is checked 4 times a day.
> Unless someone objects I will do a final image and or movie then leave things to Bill.


How do you synch with GPS? Start an app or function that uses the GPS (the way you would with a Garmin watch)?

Testing more than one watch and using different methods is often a good idea. Different people have different knowledge and may have different insights. And we often want to know how our own watch performs, even if others have a similar watch and test. So I would always be glad to see others testing Apple Watches.

Not an objection, of course. I can also understand a desire to use some of the other watch functions that require connectedness, making it hard to test standalone drift.


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## ronalddheld (May 5, 2005)

I believe starting a function the uses GPS will initiate a test for a sync.
Maybe I should test one more week....


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## wappinghigh (Dec 27, 2016)

I couldn't get my AW2 to sync via GPS in workout mode. It seems to disable "time" (a sort of little red error comes up that looks like a red iphone symbol with a cross thru it)... I confirmed it is not tracking GPS time, because my Atomic app doesn;t work in workout mode either... it lies dormant. As soon as the watch syncs again with the iphone this little error symbol goes away and also the Atomic app works again. I am suspicious it is not syncing time at all via GPS. Thoughts everyone?


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## wappinghigh (Dec 27, 2016)

ronalddheld said:


> I believe starting a function the uses GPS will initiate a test for a sync.
> Maybe I should test one more week....


Please test this. Because I couldn't get it to sync via GPS. So how are others doing it?


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## ronalddheld (May 5, 2005)

Could it be, that if you start an app that uses GPS, it would automatically sync if the time difference is great enough?


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## Bill R W (Nov 9, 2015)

wappinghigh said:


> Please test this. Because I couldn't get it to sync via GPS. So how are others doing it?


Does your watch record your route during a workout (to be viewed on your iPhone)? If so, it might show the GPS was working. I found I had to enable location services for the Apple watch workout mode on my iPhone to be able to get a route recorded.

I also wonder whether the watch might use the phone's GPS instead of its own if the phone is nearby and connected. If so, it might meant mean the watch does not synch with the GPS?

My Garmin watches synch time whenever the GPS is activated for a function. You can see this because they are not that accurate in timekeeping when the GPS is not running (in a HAQ sense). The AW2 is more accurate in timekeeping standalone, so it may be harder to see.

Would be nice if Apple had some documentation on this.

Travelling the next week and a half, so will not do more testing til later this month.


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## BarracksSi (Feb 13, 2013)

Bill R W said:


> I also wonder whether the watch might use the phone's GPS instead of its own if the phone is nearby and connected. If so, it might meant mean the watch does not synch with the GPS?


Of your questions, this is the only one I know half an answer to.

If the phone is available, yes, the phone's GPS is used. It's partly for accuracy (the phone also uses cellular triangulation and wifi network locations) but mainly for saving power on the AW. The phone's battery is a much bigger gas tank, after all.

The Atomic app wappinghigh is using may not have access to the AW's native time, but I'm just guessing. I wouldn't use it as a way to see if it's syncing via GPS. It might be more reliable to check its timekeeping over a week or two while in Airplane Mode, do a few outdoor Workout sessions to force GPS, and see if it drifts (or if its drift changes during a Workout). _I believe_ it should also log a GPS track and upload it to your phone later.

wappinghigh, the crossed-out red iPhone icon is only showing that it doesn't have a connection to the phone. It doesn't indicate a lack of connection to a time server or anything. When I'm at home and I have my phone in Airplane Mode, and my AW in regular mode, the watch did not display the red iPhone icon; but in Control Center, it showed "Connected" and a green cloud icon, indicating that it was connected to the internet. If the AW has no data connection at all, _and_ it's not in Airplane Mode, then it'll show the crossed-out iPhone icon.


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## Bill R W (Nov 9, 2015)

BarracksSi said:


> Of your questions, this is the only one I know half an answer to.
> 
> If the phone is available, yes, the phone's GPS is used. It's partly for accuracy (the phone also uses cellular triangulation and wifi network locations) but mainly for saving power on the AW. The phone's battery is a much bigger gas tank, after all.
> 
> ...


Think the green cloud icon may mean your AW2 is connecting to the internet through wifi, without using your phone. I believe that the AW2 can use wifi networks that your phone has used before, without using the phone.


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## BarracksSi (Feb 13, 2013)

Bill R W said:


> Think the green cloud icon may mean your AW2 is connecting to the internet through wifi, without using your phone. I believe that the AW2 can use wifi networks that your phone has used before, without using the phone.


100% correct.

There are exceptions where the AW won't achieve a wifi connection -- secure networks that require a login, networks that aren't using 2.4 GHz channels, etc -- but the details are still a little confusing.

It's not an issue because there's not a good way to enter login info on the AW itself, so you'd use the phone anyway.


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## chris01 (Jan 5, 2011)

Image #6 from Ronald


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## ronalddheld (May 5, 2005)

Note no leap second on the AW. I took a short movie and found an offset of about 1 second. One more image and I go to actually wearing the watch


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## Bill R W (Nov 9, 2015)

ronalddheld said:


> Note no leap second on the AW. I took a short movie and found an offset of about 1 second. One more image and I go to actually wearing the watch


So on the order of one second drift in 33-34 days, so far?


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## ronalddheld (May 5, 2005)

Bill R W said:


> So on the order of one second drift in 33-34 days, so far?


Yes taking into account the extra second. 12s/365 days is approximately 1/30 s/d which is under the 50 milliseconds "limit".


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## wbird (Feb 25, 2015)

Well yes that is the drift, but that is not the spec for the watch. The watch spec is that it will be always accurate to 50ms. Based on my math, Apple Watch has to update its time every 3 or 4 hours to stay in spec, assuming a 14ms per hour drift or less.


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## wappinghigh (Dec 27, 2016)

centisecond this is the Atomic watch app I am using. It also has an AppleWatch icon. I haven't got a clue how it is working on the watch. I am suspicious the Apple watch does *not* sync at all via Satellite or GPS but can;t prove it. Why doesn't Apple provide some explanation on this. or a means for developers to confirm this, turn it on/off within their apps?


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## wbird (Feb 25, 2015)

Check that, if it can sync to 10ms it needs 30 hours between syncs


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## wappinghigh (Dec 27, 2016)

wbird said:


> Check that, if it can sync to 10ms it needs 30 hours between syncs


 I don;t understand. I just want to walk outside with my Apple watch on and not an iphone within miles. I want to launch an atomic time app on the watch, and I want to push a "sync via satellite" button and watch the atomic atch app do just that and give me feedback that it's done and synced. I essence I want the exact same experience in GPS tie syncing on the Apple Watch2 as the Seiko Satellite Astron and the other Japanese GPS time sync watches. Cheers.


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## BarracksSi (Feb 13, 2013)

wappinghigh said:


> I don;t understand. I just want to walk outside with my Apple watch on and not an iphone within miles. I want to launch an atomic time app on the watch, and I want to push a "sync via satellite" button and watch the atomic atch app do just that and give me feedback that it's done and synced. I essence I want the exact same experience in GPS tie syncing on the Apple Watch2 as the Seiko Satellite Astron and the other Japanese GPS time sync watches. Cheers.


I don't think Apple will allow an app to do it. They already don't allow it with the phone. Letting that kind of system manipulation become accessible to an app written by God-knows-who is not a good plan for device security.

It already syncs online. That's enough, right?


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## wbird (Feb 25, 2015)

I'm pretty sure 50ms accuracy is going to be good enough for most. Knowing this is there any need to do that manual sync, just let the Apple Watch do its thing.


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## wappinghigh (Dec 27, 2016)

BarracksSi said:


> I don't think Apple will allow an app to do it. They already don't allow it with the phone. Letting that kind of system manipulation become accessible to an app written by God-knows-who is not a good plan for device security.
> 
> It already syncs online. That's enough, right?


Sure. It's more the principal of it all though. They market it as an accurate time piece. They market it as having sync with an Atomic clock. In essence it is competing in this space (as discussed on this thread) with HAQ's that do just that via Radio and GPS. It would be fair enough to know exactly how they are doing it (given the device is also independently capable of receiving GPS signals. Something which is also marketed by Apple). Cheers.


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## ronalddheld (May 5, 2005)

One should be able to ask at the Apple store or through an app now to get GPS to set the watch time.


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## Bill R W (Nov 9, 2015)

Ronald, you may be able to do an interesting test of possible GPS synching with your AW2, since it has accumulated drift and needs a leap second. 

Consider taking your AW2 out of airplane mode where it can't connect with your phone (phone with Bluetooth off and/or in airplane mode?) or a wifi network (maybe this is tricky, as the watch will use wifi networks that your iPhone has previously used -- not sure if you can turn this feature off). Then do something with the watch that uses GPS -- an outdoor walk with workout turned on or maybe a map function? 

At that point, it seems 3 things could happen -- no change to the watch's time, as it is not synching tjme with GPS; the watch adjusts to eliminate the drift, correcting its time, but not picking up new leap second data from GPS; or it fully corrects, correcting the drift and leap second. 

Given the special procedures we have been recently discussing in this forum for GPS watches to get updated leap second info and the power required for these special GPS leap second synchs, maybe it is possible that Apple did not build in GPS synching (even though it generally seems logical to provide GPS time synching, once GPS is built in). Of course, the AW2 could get the new leap second data from other sources requiring less power, as it is "connected" in ways that an MW, Casio, Seiko or Citizen GPS watch is not. The leap second was announced a while back, so your AW2 could have already had that information from sources other than GPS satellites when you put it in airplane mode last November. 

Separately, have you seen any documentation, or Apple comments, or user comments confirming the AW2 can synch time with GPS? It would certainly make sense for it to do so, but I am not sure that I have seen anyone say they have actually seen it. 

Travelling this week and next, so will not be doing much testing. Noticed my AW2 switched to the new time zone yesterday when I took it out of airplane mode. Presumably got this from my iPhone which also switched when I took it out of airplane mode.


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## BarracksSi (Feb 13, 2013)

^^^^

I think the AW can do GPS while still in Airplane Mode. GPS is totally passive and doesn't require the AW to transmit anything.

I'd just try an outdoor workout and see what happens. You won't be able to see the workout's map until it gets downloaded to the phone where you can view it in Activity -- but you'd be able to find out if it synced via GPS and got the leap second.


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## ronalddheld (May 5, 2005)

BarracksSi said:


> ^^^^
> 
> I think the AW can do GPS while still in Airplane Mode. GPS is totally passive and doesn't require the AW to transmit anything.
> 
> I'd just try an outdoor workout and see what happens. You won't be able to see the workout's map until it gets downloaded to the phone where you can view it in Activity -- but you'd be able to find out if it synced via GPS and got the leap second.


I will try remember to do it next week, after the final image.


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## Hans Moleman (Sep 24, 2007)

wappinghigh said:


> Sure. It's more the principal of it all though. They market it as an accurate time piece. They market it as having sync with an Atomic clock. In essence it is competing in this space (as discussed on this thread) with HAQ's that do just that via Radio and GPS. It would be fair enough to know exactly how they are doing it (given the device is also independently capable of receiving GPS signals. Something which is also marketed by Apple). Cheers.


It would certainly be convenient for customers. I could then easily compare the timekeeping abilities by comparing the underlying methodology.

Ronald's testing will give us an idea what's under the hood.


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## wbird (Feb 25, 2015)

Ron, at this point I'm not sure what the purpose of another image is for. You have enough data on the drift, it seems kind of a waste. If it moves a whole second more than all your previous data is worthless, this is highly unlikely based on yours and Barracksi data, or it won't move. I think you might want to just turn on the activity tracker away from your home and its wireless internet take a brief walk or ride in your car and see if it grabs that leap second.


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## BarracksSi (Feb 13, 2013)

FYI -- using Airplane Mode while running a Workout keeps the radios off -- at least the transmitting radios, Wifi and Bluetooth.

One thing some watchOS beta users were discovering _before_ the Series 2 was that some builds of the available betas of watchOS 2 could track location during an outdoor run or walk. This was happening with the first-generation AW which, you remember, did not have GPS. When the Workout got saved to the phone, a map of the route would appear.

Their best guess was that the watch was logging which Wifi networks it was able to see. Apple (and Google, and whoever else) maintains a big database of Wifi locations to use for navigation, so the AW relayed the Wifi data during sync and the phone's Activity app rendered a map.


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## ronalddheld (May 5, 2005)

wbird said:


> Ron, at this point I'm not sure what the purpose of another image is for. You have enough data on the drift, it seems kind of a waste. If it moves a whole second more than all your previous data is worthless, this is highly unlikely based on yours and Barracksi data, or it won't move. I think you might want to just turn on the activity tracker away from your home and its wireless internet take a brief walk or ride in your car and see if it grabs that leap second.


I will do that. What needs to be turned as I might have turned off the sensors, as I am not planning on using it for fitness.


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## BarracksSi (Feb 13, 2013)

ronalddheld said:


> I will do that. What needs to be turned as I might have turned off the sensors, as I am not planning on using it for fitness.


Just choose an outdoor workout (probably Walk, although you have Run, Bicycle, or Swim as other options) and go somewhere, then come back. No need to take it out of Airplane Mode.

You don't have the choice of manually switching on GPS (let's be honest here, when we in this forum talk about syncing the AW's internal clock with GPS satellites, _we're_ the outliers). If an app needs it, it should use it; and Apple's Workout app definitely uses it.


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## ronalddheld (May 5, 2005)

BarracksSi said:


> Just choose an outdoor workout (probably Walk, although you have Run, Bicycle, or Swim as other options) and go somewhere, then come back. No need to take it out of Airplane Mode.
> 
> You don't have the choice of manually switching on GPS (let's be honest here, when we in this forum talk about syncing the AW's internal clock with GPS satellites, _we're_ the outliers). If an app needs it, it should use it; and Apple's Workout app definitely uses it.


Will try it next week.


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## wbird (Feb 25, 2015)

Damn Ron building the suspense, gotta wait a week for the final reveal. I was hoping you would choose run, start it get in your car to go to work and do a 60 mph sprint for 20 minutes, and than see if your watch was back to 50ms accurate. Good luck and look forward to seeing your results.


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## ronalddheld (May 5, 2005)

Arctic air starting today. Away tomorrow and Tuesday is the first reasonable week day to try. Not certain what I have to hunt back on besides location services and the app I need?


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## dicioccio (Jul 14, 2011)

Hi ronald, since you've started this thread, I would like to know a few informations about the iWatch:
1) is it synchronisable only with an iPhone ? or is it possible to do that also with an Androind phone ?
2) is the synchronisation automatic or is necessary any action by the user ?
3) considering it only as a watch (that is not considering its "smart" abilities) what do you think about it as a watch ? in other words, how does it "feel" comparing it to an "ordinary" watch ?
4) how long the battery last in ordinary operations ? is it possible to disable all the unnecessary operations, making it to just measure and show the time ?

Thanks a lot in advance !!!


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## ronalddheld (May 5, 2005)

no you only can use an IPhone
AFAIK a user cannot do any manual syncs.
it is a smartwatch with an emphasis of health and exercise apps.
no idea since i have not worn it enough before my testing. I assume if you delet/disable some apps you could extend the battery life. I read that nightly charging is the norm.


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## BarracksSi (Feb 13, 2013)

ronalddheld said:


> Arctic air starting today. Away tomorrow and Tuesday is the first reasonable week day to try. Not certain what I have to hunt back on besides location services and the app I need?


There isn't a way to turn Location Services on or off specifically for the watch. Not that I remember, anyway; check in the Privacy settings for the phone and in the Watch app on the phone itself.

Arctic air? What, you don't own a coat?


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## ronalddheld (May 5, 2005)

BarracksSi said:


> There isn't a way to turn Location Services on or off specifically for the watch. Not that I remember, anyway; check in the Privacy settings for the phone and in the Watch app on the phone itself.
> 
> Arctic air? What, you don't own a coat?


How well do GPS penetrate a cost and gloves. I assume the watch must touch the wrist to work as you want.


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## wbird (Feb 25, 2015)

I don't know about a coat, but I did take a run, didn't end it. Got in my car, drove home and than ended it. Could have recorded my best time ever, gps worked well in my car. For this test I think you could put it on the seat next to you with the heater on full blast.


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## ronalddheld (May 5, 2005)

wbird said:


> I don't know about a coat, but I did take a run, didn't end it. Got in my car, drove home and than ended it. Could have recorded my best time ever, gps worked well in my car. For this test I think you could put it on the seat next to you with the heater on full blast.


That is good to know. No car though so only by foot. It will be tried new week when I can allocate enough time to do the job property.


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## ronalddheld (May 5, 2005)

I did an outside walk for about 1/3 of a mile. When I compared the two times they still were separated by about 2 seconds.


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## BarracksSi (Feb 13, 2013)

ronalddheld said:


> I did an outside walk for about 1/3 of a mile. When I compared the two times they still were separated by about 2 seconds.


Whenever you get around to syncing it with the phone, the walk should show up as a workout with a small map if it used GPS.

It might not show up in Activity until a day or two later (with some things, the AW isn't in any hurry to sync), but it should be there eventually.


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## ronalddheld (May 5, 2005)

BarracksSi said:


> Whenever you get around to syncing it with the phone, the walk should show up as a workout with a small map if it used GPS.
> 
> It might not show up in Activity until a day or two later (with some things, the AW isn't in any hurry to sync), but it should be there eventually.


I did not expect to see what you described, so I deleted the activity. Eventually tgevapps I would not use would be deleted, if possible.


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## BarracksSi (Feb 13, 2013)

ronalddheld said:


> I did not expect to see what you described, so I deleted the activity. Eventually tgevapps I would not use would be deleted, if possible.


Dang it. Well, go walk again!


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## gangrel (Jun 25, 2015)

BarracksSi said:


> Dang it. Well, go walk again!


Are you telling Mr. Moderator to take a hike?????


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## ronalddheld (May 5, 2005)

gangrel said:


> Are you telling Mr. Moderator to take a hike?????


Oooooooh bad idea.
I was going to resync the watch, and actually start using it. I will consider doing it


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## BarracksSi (Feb 13, 2013)

gangrel said:


> Are you telling Mr. Moderator to take a hike?????


A long walk off a short pier! Bwa-ha-ha!


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## wbird (Feb 25, 2015)

Ron, you realize you don't have to really take a walk. Just do like a some people I see do at the gym. Get a drink, sit on the equipment, hit the sauna and go home. So set it for a walk get a drink from the fridge, moderate a forum or two, get a snack from the cabinet, pick up your mail, hit the restroom and your done with you walk. Towel off, and rest up for your results.


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## ronalddheld (May 5, 2005)

BarracksSi said:


> A long walk off a short pier! Bwa-ha-ha!


No Booster Gold or JLA Detroit laughing here.


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## ronalddheld (May 5, 2005)

wbird said:


> Ron, you realize you don't have to really take a walk. Just do like a some people I see do at the gym. Get a drink, sit on the equipment, hit the sauna and go home. So set it for a walk get a drink from the fridge, moderate a forum or two, get a snack from the cabinet, pick up your mail, hit the restroom and your done with you walk. Towel off, and rest up for your results.


GPS will not received in this building, short of by a window.
I have a walk to transportation tomorrow morning. I will start that activity and stop it when I get to the station. If it works through a coat and or hooves, fine. Sync afterwards.


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## ronalddheld (May 5, 2005)

At o dark 15 I tried another walk. Strapped the watch to my wrist, set the parameters and off I went. Exceeded my goal and saved the results. Compared times and still ~2 s off. Will resync shortly.
Edit: just reconnected an the times are not identical.


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## ronalddheld (May 5, 2005)

Six hours later the watch and iPhone read the same time. Might give credence to the four times a day server check.


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## BarracksSi (Feb 13, 2013)

ronalddheld said:


> Six hours later the watch and iPhone read the same time. Might give credence to the four times a day server check.


Yup, something like that. Maybe when I synced mine (that is, forced my AW to connect to my home wifi by turning off my iPhone's radios) it was right before a regular server check, because it wasn't long (less than ten minutes, I think) before it corrected itself.


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## Bill R W (Nov 9, 2015)

ronalddheld said:


> Six hours later the watch and iPhone read the same time. Might give credence to the four times a day server check.


Was the watch in airplane mode throughout, so any change in the watch's time came from the GPS time data, not the iPhone's time or a wifi connection?


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## ronalddheld (May 5, 2005)

Bill R W said:


> Was the watch in airplane mode throughout, so any change in the watch's time came from the GPS time data, not the iPhone's time or a wifi connection?


No, that was six hours after connecting to an IPhone via BT.


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## Bill R W (Nov 9, 2015)

ronalddheld said:


> No, that was six hours after connecting to an IPhone via BT.


So that means we have no evidence yet that the AW2 synchs its time with GPS?

I was travelling the last 12 days and had my AW2 with me, along with a couple other watches. When I switched my AW2 and iPhone out of airplane mode after my flight landed, I noticed that they both found the new time zone within a few seconds. This happened both on my outbound flight and on my return flight. It would seem unlikely that both flights happened to land close in time to a regular synch time. So I wonder whether going in and out of airplane mode on the AW2 can trigger a full time synch or perhaps only a location-based timezone update (at least if the watch's paired iPhone is within range). It would certainly make sense to do at least the latter.

I had not accumulated any visible time drift on my AW2, so I could not distinguish between the two possibilities.

Plan to start testing my AW2's timekeeping this weekend.


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## ronalddheld (May 5, 2005)

Bill R W said:


> So that means we have no evidence yet that the AW2 synchs its time with GPS?
> 
> I was travelling the last 12 days and had my AW2 with me, along with a couple other watches. When I switched my AW2 and iPhone out of airplane mode after my flight landed, I noticed that they both found the new time zone within a few seconds. This happened both on my outbound flight and on my return flight. It would seem unlikely that both flights happened to land close in time to a regular synch time. So I wonder whether going in and out of airplane mode on the AW2 can trigger a full time synch or perhaps only a location-based timezone update (at least if the watch's paired iPhone is within range). It would certainly make sense to do at least the latter.
> 
> ...


Maybe just the timezone updated on the IPhone?


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## BarracksSi (Feb 13, 2013)

ronalddheld said:


> Maybe just the timezone updated on the IPhone?


The iPhone gets its location info and checks the local cellular time. I'm pretty sure that when it reconnects with the watch, it senses the difference and sends the correct time to the watch.

Speaking of flying with the AW --

There isn't a way to set the time on the watch, like if you wanted to set it to your destination time zone.

It has an option to set the displayed time ahead as much as 59 minutes, like if you're the kind of person who's habitually late and want to fool yourself into arriving early. But you simply cannot change the hour hand by itself.

You could change the phone's settings to _not_ set its time automatically, and then set it to the new time zone, but it's kind of a hassle, and it won't change the watch if you've already set either device to Airplane Mode.


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## Bill R W (Nov 9, 2015)

BarracksSi said:


> The iPhone gets its location info and checks the local cellular time. I'm pretty sure that when it reconnects with the watch, it senses the difference and sends the correct time to the watch.
> 
> Speaking of flying with the AW --
> 
> ...


I have a second time zone set to display as a complication (to use Apple's term) on several of my Apple watch faces. I set this complication (before going to airplane mode, as you need your phone to do this) to show my destination time before my flight, so I could see destination time while on the plane. When I landed and the watch switched its main time display to local time, I changed the complication to show my home time.

I have a mechanical GMT watch that I also use for travelling. It has an independently adjustable hour hand, so I set it to my destination time when I board my flight.

I agree that it would be nice if Apple watches could switch the main time displayed to your destination time while you are on a plane.


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## ronalddheld (May 5, 2005)

Bill R W said:


> I have a second time zone set to display as a complication (to use Apple's term) on several of my Apple watch faces. I set this complication (before going to airplane mode, as you need your phone to do this) to show my destination time before my flight, so I could see destination time while on the plane. When I landed and the watch switched its main time display to local time, I changed the complication to show my home time.
> 
> I have a mechanical GMT watch that I also use for travelling. It has an independently adjustable hour hand, so I set it to my destination time when I board my flight.
> 
> I agree that it would be nice if Apple watches could switch the main time displayed to your destination time while you are on a plane.


\
Yes i would find that helpful. Applke does not want a user to have that much control over the time.I suppose i can turn off the watch and after I land turn it back on with the phone to get the local time displayed.


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## Bill R W (Nov 9, 2015)

ronalddheld said:


> \
> Yes i would find that helpful. Applke does not want a user to have that much control over the time.I suppose i can turn off the watch and after I land turn it back on with the phone to get the local time displayed.


I don't think you have to turn the watch off and on to get local time automatically when you land, at least if you have your phone along. The watch will get local time on landing, once you take it out of airplane mode and your phone figures out its new location. For me on my last flight, this took only a few seconds.

I would not want to keep the watch off during my flight, as I still want to know the time, including knowing how much longer the flight will likely be.


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## ronalddheld (May 5, 2005)

Bill R W said:


> I don't think you have to turn the watch off and on to get local time automatically when you land, at least if you have your phone along. The watch will get local time on landing, once you take it out of airplane mode and your phone figures out its new location. For me on my last flight, this took only a few seconds.
> 
> I would not want to keep the watch off during my flight, as I still want to know the time, including knowing how much longer the flight will likely be.


Likely so, but it is displaying the old zone, not the new zone time in flight.


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## Bill R W (Nov 9, 2015)

ronalddheld said:


> Likely so, but it is displaying the old zone, not the new zone time in flight.


If you set one of the complications to the new time zone, it shows both, which is nice. Would be better, of course, if you could change the main time display to a new zone.


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## ronalddheld (May 5, 2005)

Bill R W said:


> If you set one of the complications to the new time zone, it shows both, which is nice. Would be better, of course, if you could change the main time display to a new zone.


I have not tried that maybe with the analog activity face?


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## BarracksSi (Feb 13, 2013)

Bill R W said:


> If you set one of the complications to the new time zone, it shows both, which is nice. *Would be better, of course, if you could change the main time display to a new zone.*


Right, that's what I had hoped to do the first time I flew with it.

But, I guess that since the default is an absolutely worry-free correct local time, it's habitual to always assume that the watch is correct -- and if I were to set it to the wrong time, or forgot that I had changed it, I'd be worse off than I would have been by setting a complication as you suggested.


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## Bill R W (Nov 9, 2015)

ronalddheld said:


> I have not tried that maybe with the analog activity face?


I have set a second time zone as a complication on two faces so far -- the analog Utility face and the Activity Digital face. Those are my favorites at this point. Suspect it can be done on some of the other faces too, but maybe not on all of them.


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## Bill R W (Nov 9, 2015)

BarracksSi said:


> Right, that's what I had hoped to do the first time I flew with it.
> 
> But, I guess that since the default is an absolutely worry-free correct local time, it's habitual to always assume that the watch is correct -- and if I were to set it to the wrong time, or forgot that I had changed it, I'd be worse off than I would have been by setting a complication as you suggested.


You may be right on it being simpler as it is.

The second time zone as a complication includes a label on the faces I have tried so far so you know what it is. Pretty easy to switch timezones as a complication with the AW app on your iPhone. Indeed, you can switch the complication to something other than a timezone when not travelling, like local weather.


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## ronalddheld (May 5, 2005)

Bill R W said:


> I have set a second time zone as a complication on two faces so far -- the analog Utility face and the Activity Digital face. Those are my favorites at this point. Suspect it can be done on some of the other faces too, but maybe not on all of them.


I will try it on a little used face.


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## BarracksSi (Feb 13, 2013)

Bill R W said:


> You may be right on it being simpler as it is.
> 
> The second time zone as a complication includes a label on the faces I have tried so far so you know what it is. Pretty easy to switch timezones as a complication with the AW app on your iPhone. Indeed, you can switch the complication to something other than a timezone when not travelling, like local weather.


I used to have a version of the Modular face with three other time zones across the bottom corresponding to distant relatives. It looked a bit like those walls-of-clocks you used to see in newsrooms.


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## Bill R W (Nov 9, 2015)

Started a time test of my AW2 today. Put it in airplane mode. No way to tell (that I know of anyway) when its most recent synch was before going into airplane mode. I plan to leave the watch in airplane mode, but still wear it some, as I would in normal life. Will not leave it on the charger, but will charge it when gets down go the 20% range on the battery.

One odd occurrence makes me wonder if airplane mode is enough to stop all connections. I have local weather set as a complication on the Activity Digital face. In the video I took after putting it in airplane mode, the watch shows 29 degrees as a temperature. The watch is still in airplane mode now a couple of hours later and has been since I started the test. But the watch now shows 31 degrees for the temperature. The watch says it is disconnected in the control center and does not show the little green cloud that is supposed to indicate a wifi connection. Does this mean there was just some delay in updating the weather from a connection/synch that happened before I put it in airplane mode? Or was/is it still connected in some fashion (and if so, would that connection also update time)? I will keep watching the temperature to see if it changes again while in airplane mode. Still 31 degrees at the nearest airport station. 

Using 400 fps video and checking 5 different second transitions (my camera will shoot only 5 seconds of video at 400 fps), the difference between the AW2 and my GPS PPS signal was 7, 8, 1, 10 and 10 frames, with the watch being slow compared to the PPS in each case. A point in time measurement to use as a baseline. This averages 7.2 frames, which is about 18 milliseconds slow compared to the GPS output. 

Not sure why one measurement was so much closer -- only one frame off GPS PPS. Compensation mechanism? Differences based on processor activity? Natural variation? Something else?

But this certainly suggests the initial time, as a baseline, is well within Apple's 50 milliseconds spec, even if I also add 1 or 2 frames worth on either side, as a range to reflect the resolution of 400 fps. 

Also shot a sequence using 60 fps video just before the 400 fps video. Less resolution. 10 transitions to new seconds. 5 were 3 frames apart (e.g., GPS changed in frame 1 and AW2 changed in frame 4), 4 were 2 frames apart, and 1 was in between. Watch again behind the GPS signal. This suggests a bit more difference than the 400 fps sequence (2.5 average frames is around 41-42 milliseconds). Assume the 400 fps sequence is more accurate because of better resolution, so will go with that.


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## Hans Moleman (Sep 24, 2007)

Bill R W said:


> Not sure why one measurement was so much closer -- only one frame off GPS PPS. Compensation mechanism? Differences based on processor activity? Natural variation? Something else?


An Apple watch is a computer. It needs to schedule everything.
Screen refreshes may or may not happen at a fixed time.

Is your watch connected?

My router has a 'DHCP clients table' button.
All computers that are connected via DHCP are listed here.
Your may need to rummage around in the router settings to see who's currently using it.


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## ronalddheld (May 5, 2005)

Bill R W said:


> Started a time test of my AW2 today. Put it in airplane mode. No way to tell (that I know of anyway) when its most recent synch was before going into airplane mode. I plan to leave the watch in airplane mode, but still wear it some, as I would in normal life. Will not leave it on the charger, but will charge it when gets down go the 20% range on the battery.
> 
> One odd occurrence makes me wonder if airplane mode is enough to stop all connections. I have local weather set as a complication on the Activity Digital face. In the video I took after putting it in airplane mode, the watch shows 29 degrees as a temperature. The watch is still in airplane mode now a couple of hours later and has been since I started the test. But the watch now shows 31 degrees for the temperature. The watch says it is disconnected in the control center and does not show the little green cloud that is supposed to indicate a wifi connection. Does this mean there was just some delay in updating the weather from a connection/synch that happened before I put it in airplane mode? Or was/is it still connected in some fashion (and if so, would that connection also update time)? I will keep watching the temperature to see if it changes again while in airplane mode. Still 31 degrees at the nearest airport station.
> 
> ...


I think some data is buffered. I know that no update could occur in my apartnent as I have no WiFi router. Keep up your testing. If you lived need me, I would have you text my watch


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## Bill R W (Nov 9, 2015)

Hans Moleman said:


> An Apple watch is a computer. It needs to schedule everything.
> Screen refreshes may or may not happen at a fixed time.
> 
> Is your watch connected?
> ...


I had hoped to disconnect the watch by putting it in airplane mode. I also turned off Bluetooth on my paired iPhone.

But I believe that airplane mode in other devices like my iPad Air2 allows wifi access these days so that you can use airplane wifi. So perhaps my AW2 is using my home wifi.

The AW2 can access a wifi network on its own (without a phone) if it was connected to its paired iPhone in the past when the iPhone accessed the wifi network. Apparently the AW2 then stores the wifi address and password used by the phone so the watch can use that wifi network without the phone.

I used home wifi earlier on the AW2 and my iPhone to test it. The AW2 would thereafter use my home wifi without my phone. But when it did this, it was not in airplane mode and the AW2 showed a green cloud symbol in the control center (as the manual said it would). I do not see that green cloud symbol now and hoped that meant I had disconnected the watch completely.

Interestingly, the watch now shows a temperature of 32 degrees, another change from 29, then 31. This certainly suggests I am still connected to something.

Will see if I can tell what the router is up to and whether it shows a connection to the AW2.


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## BarracksSi (Feb 13, 2013)

Bill R W said:


> One odd occurrence makes me wonder if airplane mode is enough to stop all connections. I have local weather set as a complication on the Activity Digital face. In the video I took after putting it in airplane mode, the watch shows 29 degrees as a temperature. The watch is still in airplane mode now a couple of hours later and has been since I started the test. But the watch now shows 31 degrees for the temperature. The watch says it is disconnected in the control center and does not show the little green cloud that is supposed to indicate a wifi connection. Does this mean there was just some delay in updating the weather from a connection/synch that happened before I put it in airplane mode?


Nope --

It loads up 24 hours' worth of weather temperatures whenever it checks in with the phone. Normally, when you use Time Travel (turn the crown while on the watch face and you can skim forwards -- it was on by default in watchOS 2, but you can choose to turn it on or off in watchOS 3), as it shows you future scheduled appointments and whatnot, it'll also show the weather as it was forecast for the same time.

But, it only looks ahead 24 hours. Any further than that is a WAG anyway. Sometimes it'll be 23 or 22 hours, but that's because it last loaded the weather forecast one or two hours ago.

After a full day of Airplane Mode, the forecast weather cache will be out of date, and you won't be getting any new weather data on the AW.


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## Bill R W (Nov 9, 2015)

BarracksSi said:


> Nope --
> 
> It loads up 24 hours' worth of weather temperatures whenever it checks in with the phone. Normally, when you use Time Travel (turn the crown while on the watch face and you can skim forwards -- it was on by default in watchOS 2, but you can choose to turn it on or off in watchOS 3), as it shows you future scheduled appointments and whatnot, it'll also show the weather as it was forecast for the same time.
> 
> ...


That's interesting. I thought I was getting an actual temperature number, updated from time to time. Forecast weather would explain what I was seeing.


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## BarracksSi (Feb 13, 2013)

Bill R W said:


> That's interesting. I thought I was getting an actual temperature number, updated from time to time. Forecast weather would explain what I was seeing.


Yeah, it's kinda cool. I had noticed the 24-hour limit when I could do Time Travel ahead until the weather complication grayed and and stopped giving any new numbers.

But, it's a quick way to see how warm it might get tomorrow. Don't need the phone for that little tidbit of info anymore.


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## ronalddheld (May 5, 2005)

BarracksSi said:


> Nope --
> 
> It loads up 24 hours' worth of weather temperatures whenever it checks in with the phone. Normally, when you use Time Travel (turn the crown while on the watch face and you can skim forwards -- it was on by default in watchOS 2, but you can choose to turn it on or off in watchOS 3), as it shows you future scheduled appointments and whatnot, it'll also show the weather as it was forecast for the same time.
> 
> ...


Where did you find out about this?


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## BarracksSi (Feb 13, 2013)

ronalddheld said:


> Where did you find out about this?


From using it, basically.

Back when wOS 2 came out, we tried different things with Time Travel and found what it could and couldn't do.


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## Bill R W (Nov 9, 2015)

ronalddheld said:


> Where did you find out about this?


The manual does not seem clear about weather forecast versus current conditions. I would have thought that weather conditions and temperature would be the actual most recent conditions the watch has received from the iPhone (or wifi?) and that it would use a forecast only for showing forecasts or for showing future conditions/temperature through time travel. I think I have time travel off on my watch.

My watch's reported weather has continued to change in airplane mode, but actual conditions (and the forecast) since I put it into airplane mode have only varied through an unusually narrow range. I will see what happens when I get to the 24 hour mark in airplane mode this afternoon.

Would be nice if the manual better explained things like this.


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## Bill R W (Nov 9, 2015)

I think BarracksSi is correct. I put my AW2 in airplane mode yesterday sometime between 1:00 pm and 1:29 pm. It continued to show a new temperature on one of my watch face complications (and the watch's weather app) periodically through 1:00 pm today. Then shortly after 1:00 pm, the field that had been showing temperature went blank and now shows two underscore characters instead of a number.

This link to Apple's website says that airplane mode turns off wireless and Bluetooth on an Apple Watch and indicates there is no way on the Apple Watch to turn on wifi or Bluetooth while keeping the watch in airplane mode (in contrast to an iPhone or iPad).

https://support.apple.com/en-us/HT204234

From a user perspective, I would like to have the watch be clearer as to when it is displaying actual current weather conditions and when it is displaying a forecast. But that is not an issue for this forum.

But for time testing, I think this means my AW2 is running on its own and not synching time. I plan to check the watch against my GPS PPS signal about once a week. Will report back to this thread.


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## BarracksSi (Feb 13, 2013)

Bill R W said:


> From a user perspective, I would like to have the watch be clearer as to when it is displaying actual current weather conditions and when it is displaying a forecast. But that is not an issue for this forum.


From Apple's perspective, I would wonder what the heck people are doing by keeping their smartwatches in Airplane Mode for days on end. 

(I did it for almost a month!)


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## Bill R W (Nov 9, 2015)

BarracksSi said:


> From Apple's perspective, I would wonder what the heck people are doing by keeping their smartwatches in Airplane Mode for days on end.
> 
> (I did it for almost a month!)


Other than testing the watch's timekeeping on a standalone basis, the only other reason I have considered is whether airplane mode would extend battery life materially.


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## ronalddheld (May 5, 2005)

Bill R W said:


> Other than testing the watch's timekeeping on a standalone basis, the only other reason I have considered is whether airplane mode would extend battery life materially.


So did I, for the good of the group.


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## Bill R W (Nov 9, 2015)

Started my first time test of my AW2 6 days ago. I put the watch in airplane mode and checked a baseline. No way to tell when the watch had last synched its time. 

Using my usual setup with 400 fps video and a GPS PPS signal (actually two now). The watch measured 18 milliseconds slow against the GPS PPS signals.

Today, 6 days later, the watch measured 73 milliseconds slow against the GPS PPS signals. This was determined using an average of 10 transitions to new seconds recorded in two five second clips. 

55 milliseconds drift in 6 days. If the drift rate stays the same, this would be about 0.3 seconds per month or a bit better than 3.5 seconds per year. Of course, not sure it makes sense to extend such a short period to a month or a year. But the watch seems to be performing well on its own so far. 

Interestingly, there is more variation between individual second transitions in a single clip than I have seen when I have tested my Morgenwerk. In the baseline measurement for the AW2, there was a 9 frame difference between the offset measurements that were farthest apart (versus the PPS signal), or 22.5 milliseconds. Today, the difference between the fastest and slowest measurements was 5 frames in each of the two clips, or 12.5 milliseconds. 

As Hans Moleman pointed out, this could reflect processing delays, as the AW2 is probably doing more stuff than my MW M1-3, even in airplane mode. Could also be related to screen refresh rates? Does anyone know what the refresh rate is for the AW2? I have not seen a spec for that. Maybe there are other sources of variability or even tester error. 

Plan to check the watch once a week for a month or so and see how it looks. Hard to leave in airplane mode, as I enjoyed several connected features in the watch when I used it on vacation earlier this month. Liked it better than I expected.


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## ronalddheld (May 5, 2005)

Accuracy/precision is a requirement for both watches. I suspect the AW is doing more in airplane mode than just keeping time. If someone at Apple would just open up a little....


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## BarracksSi (Feb 13, 2013)

ronalddheld said:


> Accuracy/precision is a requirement for both watches. I suspect the AW is doing more in airplane mode than just keeping time. If someone at Apple would just open up a little....


It just keeps doing everything that doesn't require inbound data. Track workouts, activate alarms (I used mine as a morning alarm every workday while it was in Airplane Mode), log HR measurements, etc.

I doubt the CPU has anything to do with timekeeping, though.


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## Bill R W (Nov 9, 2015)

I did another time test of my AW2 on Sunday. Used the same methods described in post #185 of this thread. 

If I average the measurements for 10 different transitions to new seconds in two five second 400 fps video clips, I find the watch was approximately 64 milliseconds fast over the 7-day period. This annualizes to around 3.2 seconds fast per year. (In the prior 6-day period it had run approximately 55 milliseconds slow, which annualizes to around 3.4 seconds slow per year.)

Combining the two periods into a single 13-day period, the slow first week is a bit more than offset by the fast second week. Overall for 13 days, the watch ran a bit over 9 milliseconds fast, which annualizes to around 0.25 seconds fast per year. 

As before, I am annualizing relatively small periods here, which could magnify any errors. 

The watch has been in airplane mode and I have not used the GPS. I have been wearing the watch during waking hours on about half of the days. I have let the battery run down to around 20-30% before recharging. As a result, I have been charging the watch every 2 or 3 days. 

Again I saw a fair amount of difference in the point-in-time measurements within a single 5 second clip. The largest difference was 19 frames (one measurement at 11 frames slow followed by one at 8 frames fast) or almost 50 milliseconds difference. Again maybe this reflects differences produced by whatever other processing the watch is doing. 

Overall, still pretty good performance, both in the largest differences between the watch's time and my GPS PPS signal (a point in time measurement) and the watch's rate over the 6, 7, and 13 day periods.


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## Hans Moleman (Sep 24, 2007)

Bill R W said:


> ... I have been wearing the watch during waking hours on about half of the days....


Keep a good eye on the temperatures the watch is exposed to.
Might come handy come explaining time.

There, I've spoiled it all for you.


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## Bill R W (Nov 9, 2015)

Hans Moleman said:


> Keep a good eye on the temperatures the watch is exposed to.
> Might come handy come explaining time.
> 
> There, I've spoiled it all for you.


A good explanation is hardly a spoiler.

I have been wearing the watch on and off while testing it, as I wanted to see how it would do in circumstances similar to how I would use the watch. That would create temperature differences. It's winter here so there are also temperature differences between home and office and times I wear the watch outside under a coat sleeve.

I have not tracked my wearing of the watch over the testing periods or other temperature changes. I wore it part time in both periods, but it is certainly possible that I wore it more in one period than the other.

I may have to try a period where I do not wear the watch and temperature is relatively constant.


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## Bill R W (Nov 9, 2015)

I did another time test of my AW2 today. Used the same methods described in posts #185 & #188 of this thread. 


If I average the measurements for 10 different transitions to new seconds in two five second 400 fps video clips, I find the watch was approximately 19 milliseconds fast over the last 7-day period. This annualizes to around 1 second fast per year.


Combining the three periods I have measured into a single 20-day period, the watch ran a bit over 28 milliseconds fast, which annualizes to around 0.5 seconds fast per year. 


As before, I am annualizing relatively small periods here, which could magnify any errors. 


The watch has been in airplane mode and I have not used the GPS. I have been wearing the watch during waking hours on about half of the days. I have let the battery run down to around 20-30% before recharging. As a result, I have been charging the watch every 2 or 3 days. 


Again I saw a fair amount of difference in the point-in-time measurements within a single 5 second clip. The largest difference was 10 frames or 25 milliseconds difference. Again maybe this reflects differences produced by whatever other processing the watch is doing. 


Still pretty good performance, both for the week and the cumulative 20 days.


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## Bill R W (Nov 9, 2015)

I did another time measurement for my AW2 today. Used the same methods described in posts #185, #188 & #191 of this thread. 




If I average the measurements for 9 different transitions to new seconds in two five second 400 fps video clips, I find the watch was a bit more than 30 milliseconds fast over the last 7-day period. This annualizes to around 1.6 second fast per year.




Combining the four periods I have measured into a single cumulative 27-day period, the watch ran a bit over 58 milliseconds fast, which annualizes to around 0.8 seconds fast per year. 




As before, I am annualizing relatively small periods here, which could magnify any errors. 




The watch has been in airplane mode for the 27 days and I have not used the GPS. I have been wearing the watch during waking hours on about half of the days. I have let the battery run down to around 20-30% before recharging. As a result, I have been charging the watch every 2 or 3 days. 




Again I saw a fair amount of difference in the point-in-time measurements in one case in a single 5 second clip. The difference was 18 frames or 45 milliseconds. Again maybe this reflects differences produced by whatever other processing the watch is doing. 




Still pretty good performance, both for the week and the cumulative 27 days.


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## adi4 (Dec 20, 2011)

Impressive, this thread convinced me to finally spring for the AW 2 to see for myself, as well as for the connected features. I will probably not be testing in airplane mode anytime soon while I'm fiddling, but may try it sometime in a couple of months. Nice to see the results so far.


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## ronalddheld (May 5, 2005)

Anyone use the AW paid app Atomic clock for timing work?


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## Bill R W (Nov 9, 2015)

I did another time test of my AW2 yesterday. Used the same methods described in posts #185, #188, #191 and #192 of this thread. 


Interestingly, the AW2's performance was not as good over the last 7-day period as in prior periods. The watch drifted about 252 milliseconds fast over the 7-day period. This annualizes to around 13 seconds a year fast. 


Combining the five periods I have measured into a single 34-day period, the watch ran a bit over 310 milliseconds fast, which annualizes to around 3.3 seconds fast per year. 


Again I saw a fair amount of difference in the point-in-time measurements within a single 5 second clip. The largest difference was 31 frames or 77.5 milliseconds difference, bigger than in prior periods. Again maybe this reflects differences produced by whatever other processing the watch is doing. 


So somewhat worse performance over the last 7 days than before. Not that bad of course. Perhaps this change could be due in part to a change in the weather here. It warmed up to daily highs in the upper 50s and low 60s for much of the period, which is unseasonably warm. Of course, the watch spent most of its time indoors, where the change is smaller. 


Cumulative performance over the 34 days was not bad, although there was more variance over the shorter periods (at least with annualized numbers).


Interested to see what others find with their Apple Watches, assuming they are willing to live without synching for a while to do a test. Understand that may be hard. There may be differences from watch to watch within the same model. 


I am going to be travelling for a few days and plan to let the watch synch before I go and bring it along. May try to see if I can get an idea of when the watch synchs and then test the synching accuracy. Alternatively, I may go for a walk with the GPS on to see if I can see any evidence of a time synch using GPS. And may do another time test later this year to see if the results are different as the weather changes.


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## ronalddheld (May 5, 2005)

I am thinking of doing another longer test. Not certain when.


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## ronalddheld (May 5, 2005)

Anyone familiar with this app: There is a NTP app for the iPhone called Gorgy Atomic Timing Clock.


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## Bill R W (Nov 9, 2015)

ronalddheld said:


> Anyone familiar with this app: There is a NTP app for the iPhone called Gorgy Atomic Timing Clock.


I had it on my iPad in the past and just reloaded it. It is not one of the 4 apps (one of which was called Atomic Clock, but was not the Gorgy one) I tested against a GPS PPS signal a while back (reported in the reference time thread).

I decided then that I preferred Emerald Time because it showed tenths of a second, it gave information on the time server connections, it showed the offset between its time and the i-device system clock, and I liked its appearance.

Gorgy does show 1/60th second intervals by lighting dots around a clock face. Presumably this is the most detail you can show on a screen with a 60 Hz refresh rate and is more detail than Emerald Time shows. It could be used with photographic or video methods to make finer measurements than apps which mere show tenths. Gorgy has now added a sound feature which I find useful for the eyeball method. (Emerald Time has a good sound feature too, beeping every second and louder on the 5-second intervals).


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## Disconnected (Dec 11, 2020)

I don't know much about apple watches, I guess that is why I am here, but iPhones have some abhorrent accuracy, I put my iPhone 5S into airplane mode AND disabled GPS, because airplane mode DOES NOT disable the GPS, after 2 hours the phone has drifted back in time by 5 minutes, 6 hours it was around 15 minutes slow. 

I then connected the wifi -- the phone immediately synchronized, because the time keeping is so horrible on iPhones I was able to track all the ways they synchronize within short amount of time, it synchromizes from Wifi, LTE, cell towers (with internet data disabled), and from GPS.

Apple watch you'd have to manually disable bluetooth and GPS, not sure if that is possible since i don't own one, because Airplane mode DOES NOT disable bluetooth and GPS, GPS does not transmit signals so it does not need to be disabled on an airplane, and bluetooth is allowed since its 2.4GHz same as wifi. Thus new apple watches will continue to synchronize via GPS, additionally they could use some ultrasound synchronization with the iphone that updates the time. 

I absolutely refuse to believe that Apple watches being perfectly in sync with each other on the table of Apple store is impressive, it is not, they are literally being synchronized every few minutes via bluetooth or GPS, and Apple probably realized they need to do it because it would just look bad if all watches showed different time and they care about presentation, this is just old people going wow over the magic of radio waves. So saying its 4 times more accurate than iPhone still means it's much worse than a $14 Casio.

How often the iPhones synchronize and what route they prefer to synchronize via i have no idea, cell towers is probably the "cheapest" way to synchronize since the pinging is constant, GPS is probably last resort.


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## BarracksSi (Feb 13, 2013)

Disconnected said:


> Apple watch you'd have to manually disable bluetooth and GPS, not sure if that is possible since i don't own one, because Airplane mode DOES NOT disable bluetooth and GPS, GPS does not transmit signals so it does not need to be disabled on an airplane, and bluetooth is allowed since its 2.4GHz same as wifi. Thus new apple watches will continue to synchronize via GPS, additionally they could use some ultrasound synchronization with the iphone that updates the time.


After all that... I'm not sure if you read the thread.

My AW in Airplane Mode drifted. It was tighter than 1 sec/mo, but it drifted, and far more than you would expect if it synced via GPS.


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## Disconnected (Dec 11, 2020)

BarracksSi said:


> After all that... I'm not sure if you read the thread.
> 
> My AW in Airplane Mode drifted. It was tighter than 1 sec/mo, but it drifted, and far more than you would expect if it synced via GPS.


It 100% syncs via GPS, what you saw could be few hours out of sync, check settings and see if you can disable the GPS specifically and do the test again, I have read several pages and then gave up after reading a ton of speculations without any data to back it up.


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## BarracksSi (Feb 13, 2013)

Disconnected said:


> It 100% syncs via GPS, what you saw could be few hours out of sync, check settings and see if you can disable the GPS specifically and do the test again, I have read several pages and then gave up after reading a ton of speculations without any data to back it up.


I spent _weeks_ with the watch in airplane mode.

(edit) Here's the graph. The jump back to zero at the end was after I switched it out of airplane mode and it re-synced with Apple's time servers.


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