Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

Workout app - inaccurate distance?

A

Andy in Embsay

macrumors member
Original poster
Apr 20, 2015
81
0
I usually run with a Garmin watch, but today I thought I'd try the workout app. Had my phone in my pocket with Strava running (can't see any other way to get the GPS track out of the Apple app). I set the app for 4 miles, but whilst I was out decided to do a bit extra and ended up doing what I know from Garmin is a 4.5m run.

Strava had 4.5m, but the watch app says 4.13m. They're both measured off the phone's GPS, so I'm unsure why the watch would be so far out?

As I can't see any way of getting the data out of the Apple app and into Strava, Garmin Connect etc I'll probably stick to running with my Garmin, but it seems odd that the data is so far out.
 
The phone's GPS was fine (as Strava was right) - so I'm wondering whether the watch was using the accelerometer and not GPS (perhaps because Strava was using it?).
 
Strava is supposed to be the most accurate of the phone apps. When I did a test of Strava against a Polar M400 I found them both the virtually the same. The problem would be when you get out of range of phone range, i.e. Off road
 
Doesn't Strava just go off the GPS track (in which case it wouldn't need a phone signal)? I know the run I did is pretty much bang on 4.5 miles, having done it literally dozens of times with a range of GPS devices, so the Strava measure is right. I wonder whether the phone's GPS can only provide data to one app at a time?
 
I did a known 5k route yesterday with my Apple Watch and it was also almost a quarter of a mile off. Runkeeper was running on the phone and had the correct distance.

In positive news the heart rate info almost exactly matched my chest strap, so the sensors seem very accurate.
 
surferfb said:
I did a known 5k route yesterday with my Apple Watch and it was also almost a quarter of a mile off. Runkeeper was running on the phone and had the correct distance.

In positive news the heart rate info almost exactly matched my chest strap, so the sensors seem very accurate.
Click to expand...

Can two GPS apps be using the GPS at the same time? I assume yes but if no, then perhaps the iPhone was only using the steps counter which might explain the inaccuracy?
 
Andy in Embsay said:
I wonder whether the phone's GPS can only provide data to one app at a time?
Click to expand...

I think this is the key question. Another forum member posted distance recordings vs another device and reported the AW being over 1/4 mile off. I've never found an accelerometer based band to be even 95% accurate.

I know some location based apps run full time in background so it would seem the iPhone's GPS should be able to communicate with multiple apps. I use a Garmin Forerunner 620 myself and was hoping to ditch it for the AW just to relive myself of the chest strap. But this doesn't look too good as I also simulatenously use a "backup" GPS based running app on my iPhone.
 
dhy8386 said:
Can two GPS apps be using the GPS at the same time? I assume yes but if no, then perhaps the iPhone was only using the steps counter which might explain the inaccuracy?
Click to expand...

I bet that's it. I'll do my run tomorrow without Runkeeper and report back if others haven't already.
 
Interesting. I did a 5K route yesterday that I run several times per week, so I know pretty much exactly every mile mark. I ran with :apple:Watch WITHOUT my iPhone, and the watch was within 0.05 miles of being accurate throughout the entire run.
 
Accelerometer calibration

I had read the the watch uses the accelerometer and calibrates with use from the phone gps. This would then allow the watch to be used while running without the phone and be relatively accurate.
 
Isn't it said that you need to "teach" your Watch about your stride before it'll be accurate enough?
 
matrix07 said:
Isn't it said that you need to "teach" your Watch about your stride before it'll be accurate enough?
Click to expand...

I thought so too, but figured I would go ahead and give it a shot without the phone. The only explanation is that maybe it took data already stored on the phone from previous runs to teach it. Also, I walked between buildings a lot on my college campus before I went on my run, so maybe it picked it up from that?
 
bmwellsokstate said:
I thought so too, but figured I would go ahead and give it a shot without the phone. The only explanation is that maybe it took data already stored on the phone from previous runs to teach it. Also, I walked between buildings a lot on my college campus before I went on my run, so maybe it picked it up from that?
Click to expand...

Or it could be a fluke. I think it needs a few more results to know for sure.
 
From the User Guide

Your iPhone GPS allows Apple Watch to achieve even more distance accuracy. For example, if you carry iPhone while using the Workout app workout icon on a run, Apple Watch uses the iPhone GPS to calibrate your stride. Then later, if you’re not carrying iPhone, or if you’re working out where GPS is unavailable (for example, indoors), Apple Watch uses the stored information about your stride to measure distance.
 
alever said:
Your iPhone GPS allows Apple Watch to achieve even more distance accuracy. For example, if you carry iPhone while using the Workout app workout icon on a run, Apple Watch uses the iPhone GPS to calibrate your stride. Then later, if you’re not carrying iPhone, or if you’re working out where GPS is unavailable (for example, indoors), Apple Watch uses the stored information about your stride to measure distance.
Click to expand...

But I had my phone with me - with Strava running on it, so my theory is that Strava used the GPS and the watch had to just use the accelerometer. That's fine, but until i can get the GPS track off the Apple app and into Strava I'll probably have to keep using my Garmin for running and cycling.
 
surferfb said:
I bet that's it. I'll do my run tomorrow without Runkeeper and report back if others haven't already.
Click to expand...

So just back from my run without Runkeeper but with iPhone. Good news is that I got the exact same distance reading as I got when I ran the same course on Friday with Runkeeper on, so it looks like the GPS can be used by both the Watch and Runkeeper. Bad news is that means that either my Watch is off by around 1/4 of a mile or my Garmin 610 is wrong.
 
Ive used strava for a cycle and the workout app and the distance was exactly the same for me.
 
Andy in Embsay said:
I usually run with a Garmin watch, but today I thought I'd try the workout app. Had my phone in my pocket with Strava running (can't see any other way to get the GPS track out of the Apple app). I set the app for 4 miles, but whilst I was out decided to do a bit extra and ended up doing what I know from Garmin is a 4.5m run.

Strava had 4.5m, but the watch app says 4.13m. They're both measured off the phone's GPS, so I'm unsure why the watch would be so far out?

As I can't see any way of getting the data out of the Apple app and into Strava, Garmin Connect etc I'll probably stick to running with my Garmin, but it seems odd that the data is so far out.
Click to expand...

Although I completely understand that accuracy is paramount for a lot of avid runners (or athletes, trainees etc) I find that being "under" calculated (and only by a small amount) is better than "over" calculating. I'd sooner have a conservative figure which will then make me work harder to achieve the actual figure I want rather than the other way around.

But that's just me.


Still watchless since April 10th. :p
 
surferfb said:
Bad news is that means that either my Watch is off by around 1/4 of a mile or my Garmin 610 is wrong.
Click to expand...


The 610 can definitely be wrong. I've had issues with other forerunner models. Garmin have released firmware updates for the 610 specifically to address accuracy issues so make sure it's up-to-date. I'd go off the iPhone/Watch over the Garmin any day.
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back