Mission Control Don't Believe The Apps

[Quantock Explorer]

I've been getting conflicting ride lengths between the Specialized Ride app and my mates using Strava.
The other day I recorded the same ride using the Mission Control app and the Ride app, starting both and finishing both at the same time. The Ride app gave me a total distance of 19.6m and Mission Control 21.4m.
I sent both data files to Specialized and received the following response:
"Both of the apps record your ride slightly differently and small differences in distance can be expected"
I don't call a difference of nearly 10% "small". I would expect better than this.
The good news from our perspective is that it looks like the Mission Control value is the more accurate one, as this is closer to the values that my mates record with Strava.

 

[Ripping g]

Hi yes I’ve noticed this and I believe that Strava is out but then again does mission recorded by the wheel distance or gps ?

 

[Quantock Explorer]

Hi yes I’ve noticed this and I believe that Strava is out but then again does mission recorded by the wheel distance or gps ?

I don’t think the app has the option to enter tire size, so I’ve always assumed that it uses GPS…

 

[Zimmerframe]

Sadly mission control only uses wheel size for speed and distance so errors are recorded. If you swap from 29 to 27 for instance it then becomes completely pointless to use it.

 

[Ripping g]

Yes there’s a option for wheel size am sure

 

[DreamensioN]

Wheel size can be set in the TCU but the LBS needs to do it. It's not something us end-users can simply change. This is the value Mission Control reads.

 

[Supratad]

4 years from now....in a pub somewhere amid the post-ride badinage...
[thought ballon]"hmm, I could interject here with a story of a lovely ride I did near the summer solstice, but I can't be certain if it was 19.6 or 21.4 miles. Best say nothing. ... ... though I could just say it was a 20 miler."[/thought balloon]

 

[boBE]

I changed my SL from 29 to 27.5 and the speed/distance as reported by Mission Control was way off. My LBS adjusted the wheel diameter and it is accurate now.

 

[Quantock Explorer]

4 years from now....in a pub somewhere amid the post-ride badinage...
[thought ballon]"hmm, I could interject here with a story of a lovely ride I did near the summer solstice, but I can't be certain if it was 19.6 or 21.4 miles. Best say nothing. ... ... though I could just say it was a 20 miler."[/thought balloon]

I get your point, but where would online forums be without us pedants?

 

[Jersey Skier]

The mileage reported by my Gen 3 TCU, the Specialized App and my Garmin are never the same. Fun rides anyway.

 

[Supratad]

I get your point, but where would online forums be without us pedants?

Fora, you mean?

 

[Mikerb]

MC computes distance by multiplying wheel diameter( as set in MC which could be right or wrong and either way is not exact since you can use anything from 2.3 to 2.6 tyres with different tyre wall heights and tread depth........) by wheel revolutions. Some distance may actually be covered without wheel revolution...e.g if you skid . The majority of non dedicated GPS devices measure distance by recording Tracking Points ( TP). Depending on the GPS chip those TPs can be anywhere from 10 TPs per second on a good chip to 1TP per second or even 1TP every 5 seconds for the poorest. Any deviation of track between tracking points will be straightlined so distance will be underestimated..........any temporary loss of GPS signal or transfer of reception from one set of satellites to another set will show as a straight line between TPs. Some GPS chips also take no account of elevation so the distance measured between the top and bottom of a hill will be inaccurate proportionate to the % incline. Me and my mate both use Stava...obviously on different phones. His total distance is always marginally less than mine........so it is either the difference in the GPS chips in each phone or he is cutting the corners on every gravity run

 

[Quantock Explorer]

Fora, you mean?

?

 

[Tim1023]

I've been getting conflicting ride lengths between the Specialized Ride app and my mates using Strava.
The other day I recorded the same ride using the Mission Control app and the Ride app, starting both and finishing both at the same time. The Ride app gave me a total distance of 19.6m and Mission Control 21.4m.
I sent both data files to Specialized and received the following response:
"Both of the apps record your ride slightly differently and small differences in distance can be expected"
I don't call a difference of nearly 10% "small". I would expect better than this.
The good news from our perspective is that it looks like the Mission Control value is the more accurate one, as this is closer to the values that my mates record with Strava.

It's quite possible that both figures are correct!
Making the assumption that both are measuring accurately, but different things, namely the rotations of the wheel and the GPS positioning as mentioned above, we hit a fractal issue.
The wheel rotations measure all the minor meanders around the straight lines between GPS points that Strava measures. It's like the question of how long is a coastline. The more accurately (finely) you measure it, the longer it gets.
See: