Strava accuracy

[T-Rex]

I got all excited yesterday when I set a new PR down Luge at Stromlo, normally about a 3 minute segment for me, descending and lots of berms to rail for those who don’t know it, did a 2:43 according to Strava. I got even more excited when I checked riders I follow and saw I was only 1 second behind Junior’s PR. Then I had a reality check.... fat, scared middle aged joke gets within one second of a EWS racer..... maybe not.

So I did it again today, pushing just as hard, same lines, and I was back to low 3 minutes, third best time ever, including the 2:43.

Has anyone else experienced Strava giving weird times for the same stage? I was using my phone, not my Garmin, if that matters.

 

[stirk]

Probably connected to GLONASS on the 'quicker' segment, you got performance enhanced!

 

[Elbo]

Could've been what @stirk said. Consumer level GPS is only accurate to 10-15m, and depending on tree cover, number of satellites available, and other obstructions, it only takes a dropout or glitch to suddenly skip 30m ahead or shorten a berm

I use GPS every day in Surveying and we get 20mm accuracy. Surprisingly the GPS still gives reasonable results under certain types of trees like Pines or deciduous trees, but under gum trees, the lock quality blows out considerably or it loses lock completely.

 

[Kerplunk]

Click the “analyze effort” link on the segment and have a look for any glitches or straight lines in the speed. When you have a flat line the gps has dropped out and strava has made the rest up. If you check out the top placed cup holders it is a very common occurrence. I know guys who run both the phone app and their gps at the same time on a ride and pick the device that gives the most favorable result..

 

[slimjim1]

Forget it...I cracked the top 10 on luge using the Iphone, not even close to my best effort down there.

It's no good over short segments, or segments with a sharp corner near the beginning or end. Have a look at the longer segments and you'll start seeing the same names pop up in the top ten. All the shorter segments are guys using phones, GPS watches or cheap garmins who got lucky.

This was one of the reasons I got a GPS with 1 second recording and GPS/Glonass (because I wanted at least somewhat accurate times), along with battery life and navigation.

 

[Flow-Rider]

What Kerplunk said, easy to pick when you know what to look for. Most strava activities are out a few seconds between devices but they usually error at the start and end of segments where they cut the segment short and you end with a fast PR.

 

[DMan]

Just make sure you get GPS and barometric or your elevation gain is all out too.

 

[kten]

I've found strava remarkably innaccurate depending on the device it is being used. In our group we have phones, garmin 520's and garmin watches being used with strava and on a 20km ride the differences can be significant...like 200m difference in elevation, 1.5km total distance difference not to mention large segment anomolies that create a little banter when the slow guy at the front of the trail snake gets the best time by a margin when we hit the end lol

 

[Isaakk]

Had a strava run the other day spike at a peak speed of 55kmh. Whilst run did feel fast, and I was pushing for that run (got PR)... I sure as shit didn't hit 55kmh when the avg for the top guys is 32kmh on a very pedally and flat track.

That was with (android) phone in pocket, have been thinking about picking up one of those fancy Garmin watches, wonder if that would help with accuracy?

 

[Kerplunk]

I have been on a few rides where I had the fastest time of the day yet rode with blokes who bombed down and were waiting at the bottom.. All of us on iphones.

 

[T-Rex]

Click the “analyze effort” link on the segment and have a look for any glitches or straight lines in the speed. When you have a flat line the gps has dropped out and strava has made the rest up. If you check out the top placed cup holders it is a very common occurrence. I know guys who run both the phone app and their gps at the same time on a ride and pick the device that gives the most favorable result..

Good tip Kerplunk. The segment starts right where you exit the bridge. The 2.43 shows me slowing which makes no sense, as in reality I’m accelerating into that fast left hand berm. Upon further digging, I found a 2.46 on my race run at the Superflow last weekend , and the speed profile looks sensible at the start.

What I don’t get is why it can’t figure out the elapsed time from the time stamps on the signals at the start and end of the segment. Maybe the bridge is interfering with the signal at the start.

Next time I will use my Garmin and compare.

 

[hifiandmtb]

This thread delivers.







...confirmation that leaving Strava was good for me

 

[carpetrunner]

Strava on an iPhone is for roadies.

Strava for MTB is useless without a speed[distance] sensor,
too much changing of direction and signal interruption from tree cover.
The speed/distance sensor data helps your device to make a better guess when the signal drops out.

- carpetrunner

 

[brendonj]

nothin new here. There was a short section i sessioned back in the day cause i liked it and wanted to get a good time (top of vietnam in the old language at Cootha). A mate who did well in the aus Enduro saw me once and said i was mad the speed i was going. But i could never get close to the best time by about 50%. They were xc riders riding down the adjacent fire trail 5 metres away.

And my one “real” KOM at Cootha was done on an overcast day and didn’t feel extra fast.

 

[ozzybmx]

Dont know if its changed but up until a couple of years ago, a telephone only recorded a GPS position every 3 seconds, a Garmin records every second, so mixing that with GPS drift, you could be starting a segment 5-6 seconds out and 30 meters late or early.
Its not accurate at all but if you want the best possible gauge, use a bar mounted GPS unit like Garmin, Wahoo ect.

 

[stirk]

What's wrong with just checking the time you start a ride and then check the time again when you finish the ride. That's what I do, extra piss breaks are factored in too so if I want a KOM I just drink less water so less piss breaks. You know when you nail a ride that's all that matters.

 

[Isaakk]

What's wrong with just checking the time you start a ride and then check the time again when you finish the ride.

Eh, I like being able to check segments. More for PRs than overall results too - have already resigned myself to the fact that I'll get eclipsed by the local speed demons.

 

[slimjim1]

a Garmin records every second

Not all of them...I've seen some shockers from people using 520s/530s. May as well use an Iphone 3.

 

[ozzybmx]

Not all of them...I've seen some shockers from people using 520s/530s. May as well use an Iphone 3.

They might have them set on smart recording rather than 1 second, smart only records a data point when it detects a change in elevation, speed, HR or direction.
Regardless, they are only accurate over distance, short segments are pretty random.

 

[Hey]

Usually get faster times when it’s cloudy. Strava ain’t that accurate. It’s ok for tracking your rides and times sometimes. If you buy into it more than that and take it as fact, you are fooling yourself.