Accuracy of Strava vs Suunto, Garmin etc?

[dunndog]

I'm not a big strava head, so I don't know if this is easily explained or not.. but I went for a leisurely ride with a mate on Saturday, doing the extended main loop at Wombat. We rode together, and finished where we started. I had strava on my phone in my pocket, he wore his Suunto Ambit 2 watch.
So at the end of the ride, my number were 16.9km, 203m gain, in 1:17. While his stats were 17.7km, 278m gain in 1:15:55. So there's a 1 minute discrepancy which is possible as that's actual moving time, but then there's 75m difference in gain and 800m in distance, both quite a lot considering the relatively small numbers.
Which one is likely to be more accurate and why? Does this mean using strava on your phone is a waste of time? Or am I missing something?

 

[Comic Book Guy]

A gps has a 3m horizontal accuracy and this blows out to 30m for the vertical accuracy. So the difference in height readings doesn't surprise me. Also, there are so many factors that affect performance that significant differences in results between gps units is normal. Some phones (I'm looking at you Samsung) have poorly implemented gps.

I would suggest that having the unit in your pocket is the most likely cause of the distance difference. Your mates watch would've had a much better view of the sky and therefore better signal reception.

CBG.

 

[Nautonier]

I'm not a big strava head, so I don't know if this is easily explained or not.. but I went for a leisurely ride with a mate on Saturday, doing the extended main loop at Wombat. We rode together, and finished where we started. I had strava on my phone in my pocket, he wore his Suunto Ambit 2 watch.
So at the end of the ride, my number were 16.9km, 203m gain, in 1:17. While his stats were 17.7km, 278m gain in 1:15:55. So there's a 1 minute discrepancy which is possible as that's actual moving time, but then there's 75m difference in gain and 800m in distance, both quite a lot considering the relatively small numbers.
Which one is likely to be more accurate and why? Does this mean using strava on your phone is a waste of time? Or am I missing something?

I used to use a Gamin for Strava and it seemed to be less accurate than the iphone - especially in dense forrest. Elevation data is terrible on phones though (always adds about 20%), whereas on something like a Garmin it's very accurate.

 

[Moggio]

Using an old Samsung phone for my strava at my local trails a lot for my personal monitoring of fitness, I have no idea how accurate it is to reality or other devices, I would assume not terribly. However it is surprisingly consistent with itself providing similar readings for distance and height over multiple rides of the same trails.

 

[Flow-Rider]

You can get Strava to correct the elevation gain. I can't honestly tell you which unit is more accurate but phones play up a lot due to interference. It's not uncommon that 2 measuring devices will give different totals. One of the reasons I have been told is that it's from the undulations and corners in the trails due to the devices pinging in different locations on the trail.

 

[dunndog]

75 m elevation difference over 200 odd meters is a lot though!! So the best you could do is mount the phone to the bars I guess?

 

[findbuddha]

If you want more accurate elevation data you're better off using a device with barometric altimeter rather than GPS based elevation.

 

[The Duckmeister]

Strava itself doesn't take the measurements, it's only a data storing platform and its information is only as good as what's being fed into it. Phones are notoriously less accurate than dedicated GPS receivers.

 

[dunndog]

Strava itself doesn't take the measurements, it's only a data storing platform and its information is only as good as what's being fed into it. Phones are notoriously less accurate than dedicated GPS receivers.

Yeah bang on, I pretty much figured it was the difference between using a phone and a gps device. Still, I'm sure a ton of people use their phones, and are getting data that isn't only a bit out but potentially WAY out. I do have a megellan gps unit, might take that next time to compare as well.

 

[caad9]

Phones are a handy tool for close fought segments, they will happily wander and lose valuable seconds in the scrub.

MTB segments in the bush are very dubious at the best of times

 

[ozdavo]

This is why wheel mounted speed sensors are still important with gps based devices in the bush. A gps can't correctly follow tight twisty terrain with dense canopy coverage.

Sent from my SM-G900I using Tapatalk

 

[ozzybmx]

Up until the end of last year, Strava used a common database to work out your elevation when you uploaded using a device with no Barometric Altimeter (Phones ect) This was full of holes and elevation jumps that gave phone users as much as double the elevation for rides that took in some roads/trails. There was one trail here in Adelaide called the PWT (Pioneer Womens Trail) that you could have "Everested" in about 4 hours using your phone, it even gave you 110m of climbing for descending the trail.

https://support.strava.com/hc/en-us/articles/115000024864

They are now using their own database of uploaded rides and if they have no data for a certain trail, they will call on the old database for that section.

At the start of 2017, everything was pretty equal on GPS v Phone... but I'm starting to see lumps and bumps appear in rides again, flat roads with 5-10m bumps on them. Great idea Strava, but I'm starting to think their great idea might not work.

Also remember that a telephone only records a point every 3 seconds, versus a Garmin for example, which records every 1 sec. So when hitting a short segment, the phone 'could' give you about a 5 second advantage (3 secs on either end) or a 5 second disadvantage.

I have also heard, but not experienced as I only use Garmin Connect as a medium to send the ride straight to strava using WiFi/Bluetooth, that Connect has started chopping rides to what their database thinks the distance should be. People who have went for a 100km ride, having to ride around the block to click over 100.1km, uploaded via Garmin Connect and the ride sent to Strava was only 98.5km.

 

[slimjim1]

Phones are a handy tool for close fought segments, they will happily wander and lose valuable seconds in the scrub.

MTB segments in the bush are very dubious at the best of times

Absolutely. Shorter mtb segments pretty much need to be completely disregarded (Strava should set a minimum distance IMO). There's usually 1 or 2 top times set by some random gumby which are just plain wrong, with the average speed sometimes listed as 100km/h+ for example.

Longer segments do tend to be reasonably consistent I have found, usually it's the same names appearing in the top 10.

I have used GPS and phone and the GPS follows tight twisty trails so much closer than the phone its not funny. The phone also tends to overestimate elevation gain.

 

[silentbutdeadly]

Most of the data we produce about our rides on our little widgets are merely approximations. An unreliable memoir...if I can steal the expression. Then we give it to Garmin or Strava or both and they reinterpret it on our behalf. And suddenly our unreliable memoir has become a cinematic piece of interpretive dance...

If you want a better story then get better equipment and engage a better director. However, the former is expensive and the latter is still to be found. And I've got used to the bullshit I've been watching this last few years...

 

[anton8]

This might help with accuracy -

https://bad-elf.com/pages/be-gps-2300-detail