Why does my AW always under report distance?

[dj1891]

This is somethings that has always annoyed me, and why when I run or hike I use both an AW and a Garmin.

The excuse used to be “The watch uses the phones gps” of course this changed from the 8 on and my distance is still always short and in term means pace is also slower.

For example did a 10k race on Sat, 9.84km was what Apple report, Garmin with multiband is always slightly over 10.02km was what it reports. I usually do parkrun on Saturday, 5k Apple = 4.92km Garmin 5.01km.

Anyone else have this problem or know why it happens?

 

[cubodado]

Apple uses a mix of pedometer and GPS, the app should be calibrated. In my case it seems quite precise on open air but slower around 10% in tunnels.

Calibrate your Apple Watch for improved Workout and Activity accuracy - Apple Support

You can calibrate your Apple Watch to improve the accuracy of your distance, pace, and calorie measurements. Calibrating your watch can also help it learn your fitness level and stride, which improves accuracy when GPS is limited or unavailable.

support.apple.com

 

[Howard2k]

1) Which watch?
2) How do you know that the Garmin is correct?

 

[NME42]

My AW5 did slightly underreport too. My AW7 and Ultra 2 are spot on. Could also be a watchOS update that changed that, not sure. Checked the distance they report with several maps tools and they are perfect. My earlier Garmins overreported slightly and had larger deviations on the same routes. My U2 is typically within a range of 0-30m deviation on a 10km run when I run the same route.

 

[dj1891]

1) Which watch?
2) How do you know that the Garmin is correct?

SE2, well the Garmin is a 255 using multi band and races are generally measured to correct distance

 

[cubodado]

Unless you follow the blue line and you don’t have to change often your path due to other people in a race the distance should be slightly higher at the end, in my experience around 1%.

 

[smirking]

Anyone else have this problem or know why it happens?

I have a Fitbit Sense and it uses my iPhone for GPS. I have the same problem, but it's most noticeable when I do a run that has a lot of turns. That would be the first leg of my normal route. I'm always 5 to 10% short. Other parts of that route are almost entirely straight and it's usually very close to being spot on.

When I first noticed this, I thought maybe it was correct and I was cheating by cutting the corners. To test this out, I started running only in straight lines and when I needed to turn, I'd do sharp 90 degree turns.

Nope, it was still off by almost the same margin. When I look at my run map, I see that it still thinks I'm making lazy swooping turns that clip off anywhere from 5 to 20 stride lengths of distance. I also notice that when I'm making a lot of turns, the GPS tends to show me weaving back and forth like I'm drunk.

So in my case, I think it's because it's badly misjudging my turns.

 

[Howard2k]

SE2, well the Garmin is a 255 using multi band and races are generally measured to correct distance

So really - "Why is the multi band GPS watch more accurate than the single band GPS watch?"
Because one is multi band?

 

[xraydoc]

As far as I can tell, my Ultra 2 on-watch GPS is pretty accurate — definitely not in the 5% error range.

 

[Jackbequickly]

I have driven the route that I run and my Ultra 2 is pretty darn accurate.