Took the AW Series 2 on its first run & swim today with disappointing results

[exxxviii]

Doesn't the AW rely purely on GPS? This is usually bad in built up areas or where there are line-of-sight obstructions. Phones, however, use aGPS and aGLONASS, so they are triangulating off cell phone towers and WiFi signals around you to compensate, hence the higher accuracy. On top of that, the iPhone learns frequently visited locations, making it more accurate.

True, the iPhone has more methods for location determination. However, extrapolations about accuracy are largely hypothetical. Apple does not state whether the iPhone attempts to use WiFi or cellular to assist real-time GPS calculations. My hunch is those lack the precision and are too slow for the real-time accuracy that run tracking requires. GLONASS is the Russian satellite system, which does aid accuracy. However, in my years of experience running with and without GLONASS watches, I have not noticed any accuracy differences. (Both have been around 0.02 miles standard deviation on my 5 mile runs.)

Finally, the Apple iPhone GPS tracking for running is significantly less accurate than my dedicated GPS running watch. So, whatever Apple is doing for GPS in the phone, it is not that good compared to precision units. Therefore, I would not assume that the watch is any better or any worse than other devices.

Edit: Here are some comparative data points of two different devices, with and without GLONASS, on the exact same course. Unfortunately, I do not have any recent data with any Apple devices, because I stopped carrying watch or phone on this route a while ago. My hunch is that the difference between the means is partially from the number of observations, but the two are pretty freaking close regardless.

Old device, no GLONASS

• Mean: 5.066 miles
  
• Std. Dev.: 0.016 miles
• Observations: 164

New device, with GLONASS

• Mean: 5.074
• Std. Dev.: 0.016
• Observations: 34

 

[deeddawg]

Doesn't the AW rely purely on GPS? This is usually bad in built up areas or where there are line-of-sight obstructions. Phones, however, use aGPS and aGLONASS, so they are triangulating off cell phone towers and WiFi signals around you to compensate, hence the higher accuracy. On top of that, the iPhone learns frequently visited locations, making it more accurate.

Couple of corrections here:

#1 - assisted GPS isn't what you describe; tower triangulation was something in years past with phones that didn't have GPS chips. It also isn't the old system where the location calculation was offloaded to compute equipment at the tower or on the carrier's network. What it *is* today in fact is that the towers will provide the current ephemeris to the phone, aiding its ability to achieve a faster initial lock.

#2 - wifi based location sensing isn't part of GPS, but does provide substantial accuracy improvements inside buildings, as well as very fast positioning

#3 - standalone gps devices aren't nearly as bad as you imply. I've used standalone GPS running watches for years and while they do have issues in "urban slot canyons", they generally do quite well outside that environment. As I don't own an AW2, I can't say whether its GPS hardware is on par with Garmin or Polar or the other gps sports watches. I'd be surprised if Apple didn't put in hardware on par with these others.

#4 - GLONASS primarily aids users at higher lattitudes where the GPS satellite constellation is lower to the horizon. (also remember these are constellations of many satellites orbitting twice a day; they're not geosynchronous satellites sitting in one spot relative to the surface)

 

[Julien]

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[scriptkitten]

i had my first major watch/phone discrepancy today.

i ran a route that i mapped out on my computer as 7.5m

i used the nike + app on my PHONE during the run and it measured the run as 7.5m and my pace was 8:39
i ALSO used the apple workout app on my watch to track the run (theoretically it would be using the phone GPS since my phone was in my bra, right?). my watch tracked the run as 7.27m and pace 9:02.

i shut off the runs within seconds of each other

when i compare the nike map with the apple map, the app map has quite a few dotted sections where it looks like the gps dropped. did the nike app assume i was running through the areas where the GPS was dropped? and Apple Workout assumed I took a nap and magically transported further ahead in the route?

really annoying.

 

[exxxviii]

i used the nike + app on my PHONE during the run and it measured the run as 7.5m and my pace was 8:39
i ALSO used the apple workout app on my watch to track the run (theoretically it would be using the phone GPS since my phone was in my bra, right?). my watch tracked the run as 7.27m and pace 9:02.

I could see that happening if the watch and phone BT connection failed for a few minutes, and the watch either captured no distance or tried to use steps to approximate.