Losing faith in Strava accuracy
steadyrollingman
Posts: 90
I've just synced up my Garmin Edge 1000 this week, but thru force of habit have been recording the ride on iPhone at same time. What's very noticeable is that there's a significant discrepancy between the data - one segment was recorded as a PR on one device, and a third-place on the other. There was even a difference of four seconds recorded on one segment that I covered in about 1.22, though most differ by about a second. That's the sort of margin of error that can put you in the Top 10 or keep you outside the Top 50... So I'm beginning to think that most KoMs should be taken with a pinch of salt...
Now I just need to work out which duplicated rides I should delete so as not to drop down the leaderboards...
Now I just need to work out which duplicated rides I should delete so as not to drop down the leaderboards...
Job: Job, n,. A frustratingly long period of time separating two shorter than usual training rides
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[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630099#p19630099]steadyrollingman[/url] wrote:
So I'm beginning to think that most KoMs should be taken with a pinch of salt...
A couple of years ago Strava changed its algorithms to favour its mobile app, so you are indeed right any segment you want recorded make sure its on a mobile phone rather than a Garmin etc.I'm sorry you don't believe in miracles0 -
You need to calibrate it on the road to Damascus, that's how St. Paul got his faith back...left the forum March 20230
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The Strava app only records data point every 3 or 4 seconds. You can set the Garmin to record every second. If you do that then the Garmin is way more accurate.
Due to this and the way Strava calculates if you go through the start/end points of the segment (there is a allowable distance error to cater for GPS innacuracy) the results for shorter segments are a lot more suspect than for longer segments as on longer segments the errors are minimised due to their reduced influence over a longer period of riding.
If you use Veloviewer you can see the recorded length of a segment every time you have gone through it. Each time has a different length. This is a good indication of where some of the errors creep in.
This explains the issues well: http://blog.veloviewer.com/41mph-the-evidence-against-the-sunday-times-article/0 -
There is a fair amount of anomalous data on there. This one for example
https://www.strava.com/segments/4534435?show_waiver=10 -
Haha yeah, I wrote that post before I'd even seen the leaderboard from this seg from last night's ride: https://www.strava.com/segments/9130284?filter=overall
Amazing how you can average 180mph with a max speed of 18mph, innit? Certainly helps explain how I knocked 3sec/15% off a short road section PB while on the mountain bike though.
As for Strava changes 'favouring' the iPhone, it seems there's no one device that is regularly 'faster' unfortunately - obviously depends when the signal kicks in. But given I have cadence and HRM sensors tied up with the Edge, it makes sense to start using that one in future. And I just realised my settings on the Edge were set to 'smart' for GPS. Have changed to '1 sec' now - will do a couple of rides and see if the difference is still as marked before I stop using the iPhone altogether. I've a handful of Top 50 spots but am almost certainly never gonna get any road KoMs anyway, so abandoning what may be the less accurate/most generous device is probably irrelevant as long as I can gauge my own progress ...Job: Job, n,. A frustratingly long period of time separating two shorter than usual training rides0 -
Strava/Garmin aside, The problem is that a segment that lasts 1-2 min is pointless per se... you can easily go 4-5 sec faster just because a lorry overtakes you or slower because a lorry crosses you the opposite direction, which is the reason why there are no time trials of that length.
I suggest the OP targets some more meaningful segments if he has to target any...left the forum March 20230 -
Yeah, I mean the non-specific distance is obvious, as the length of my rides or various segments of the same course (commute) vary slightly from day to day. But that certainly shouldn't apply to two devices on the same bike! I'm beginning to think that, with a few exceptions, getting a KoM may often be just as much a matter of luck as it is strength, fitness and a favourable wind...Job: Job, n,. A frustratingly long period of time separating two shorter than usual training rides0
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The reliability of the analysis is reflected in the price.
Of free (or even Premium) Strava, I assume you mean, not the exorbitantly expensive Edge 1000..,Job: Job, n,. A frustratingly long period of time separating two shorter than usual training rides0 -
[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630206#p19630206]steadyrollingman[/url] wrote:The reliability of the analysis is reflected in the price.
Of free (or even Premium) Strava, I assume you mean, not the exorbitantly expensive Edge 1000..,
Yes, I don't even know what software packages are available to buy to be honest. Pretty sure the pros don't use Strava to process their power meter data tho'.- - - - - - - - - -
On Strava.{/url}0 -
The interest for this thread reflects the state of mankind, I fear... :?left the forum March 20230
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It seems everyone now needs to write a narrative for their daily rides. What is that about?I'm sorry you don't believe in miracles0
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I think most mobile based logging applications are going to be inherently inaccurate when compared to a dedicated device over the same route. Mobiles are good for the basics but they are a 'Jack of all trades, master of none' when it comes to cycling.---
Sensa Trentino SL Custom 2013 - 105 Compact - Aksium Race0 -
[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630099#p19630099]steadyrollingman[/url] wrote:I'm beginning to think that most KoMs should be taken with a pinch of salt...
This0 -
As others have said, the phones often only record every 3 seconds.
I wrote a program once that took my Garmin file (time recorded every second) and split it into 3 separate files. The 3 files each took 1 third of the track points (1st file=1st, 4th, 7th, 10th etc. 2nd=2nd, 5th, 8th, 11th etc. 3rd=3rd, 6th, 9th, 12th). I then loaded the 3 files into Strava. On one short second which originally took 30 seconds on the Edge the times for the 3 inaccurate files ranged from 26 to 31 seconds because Strava was taking different segment start and end times.
If you are cycling at 20mph you will cover 8.94 metres per second. If the phone only records time every 3 seconds you may travel over 27 metres per recorded time. Throw into the fact that GPS is not 100% accurate it means that Strava doesn't really know when you started and ended a segment and can only guess it based on the trackpoint in your file that first gets close to the start and end of the segment start/end.0 -
The interest for this thread reflects the state of mankind, I fear... :?
What, the interest in getting fitter? Surely that's why 90% of us are on bikes in the first place? The world would be a much better/healthier place if more people were interested in Strava and less busy shoving fast food down their necks all day...Job: Job, n,. A frustratingly long period of time separating two shorter than usual training rides0 -
[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630674#p19630674]steadyrollingman[/url] wrote:
What, the interest in getting fitter? .
No, the interest in accurate recording of half a mile long segments on Strava....
It does reflect the state of mankind: i.e. caring about completely pointless things...
left the forum March 20230 -
you need a spin in the total perspective vortex mate. nothing is irrelevant because everything is.- - - - - - - - - -
On Strava.{/url}0 -
[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630674#p19630674]steadyrollingman[/url] wrote:
What, the interest in getting fitter? .
No, the interest in accurate recording of half a mile long segments on Strava....
It does reflect the state of mankind: i.e. caring about completely pointless things...
That's pretty much all sport summed up and dismissed in one sweeping statement then... I for one think the world would much be a poorer place without Hugh Porter getting way overexcited about someone knocking 0.001 off the world record for track sprinting - which is effectively the same thing as setting KoM on a short Strava segment, bar all the dozens of variables...Job: Job, n,. A frustratingly long period of time separating two shorter than usual training rides0 -
[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630860#p19630860]steadyrollingman[/url] wrote:which is effectively the same thing as setting KoM on a short Strava segment, bar all the dozens of variables...
it isn't... your effort is completely pointless and I already explained why in a previous post. A 1 minute long Strava segment on open roads is not something worth chasing, let alone going on about it because the rudimentary technology you have to record time gives unreproducible results.
If timing a 1 minute effort on the road was a meaningful enterprise, there would be half a mile time trials.
All I have seen similar is a "bicycle drag race" in a closed circuit, where max speed over a speed gun is the goalleft the forum March 20230 -
[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630293#p19630293]SloppySchleckonds[/url] wrote:It seems everyone now needs to write a narrative for their daily rides. What is that about?
Or weather reports that the met office would be able to produce a 5 day outlook from.0 -
[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630293#p19630293]SloppySchleckonds[/url] wrote:It seems everyone now needs to write a narrative for their daily rides. What is that about?
Or weather reports that the met office would be able to produce a 5 day outlook from.
I'm sorry you don't believe in miracles0 -
[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630099#p19630099]steadyrollingman[/url] wrote:That's the sort of margin of error that can put you in the Top 10 or keep you outside the Top 50... So I'm beginning to think that most KoMs should be taken with a pinch of salt...
Now I just need to work out which duplicated rides I should delete so as not to drop down the leaderboards...
:roll: :roll:
Or come to the realisation that Strava segments are meaningless...VO2 Max - 79 ml/kg/min
W/kg - 4.90 -
[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630099#p19630099]steadyrollingman[/url] wrote:That's the sort of margin of error that can put you in the Top 10 or keep you outside the Top 50... So I'm beginning to think that most KoMs should be taken with a pinch of salt...
Now I just need to work out which duplicated rides I should delete so as not to drop down the leaderboards...
:roll: :roll:
Or come to the realisation that Strava segments are meaningless...
this x 10000.0 -
[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630099#p19630099]steadyrollingman[/url] wrote:That's the sort of margin of error that can put you in the Top 10 or keep you outside the Top 50... So I'm beginning to think that most KoMs should be taken with a pinch of salt...
Now I just need to work out which duplicated rides I should delete so as not to drop down the leaderboards...
:roll: :roll:
Or come to the realisation that Strava segments are meaningless...
Meaningless in the greater scheme of things, sure, but Strava got me cycling at least twice as much as I did before, and I know others that are the same, so not meaningless for me......0 -
[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630099#p19630099]steadyrollingman[/url] wrote:That's the sort of margin of error that can put you in the Top 10 or keep you outside the Top 50... So I'm beginning to think that most KoMs should be taken with a pinch of salt...
Now I just need to work out which duplicated rides I should delete so as not to drop down the leaderboards...
:roll: :roll:
Or come to the realisation that Strava segments are meaningless...
Meaningless in the greater scheme of things, sure, but Strava got me cycling at least twice as much as I did before, and I know others that are the same, so not meaningless for me......
I am not against Strava per se... it has its merits... a huge database of GPX mapped rides easily accessible by all, a bit of healthy competition up popular segments, whether that is the Alpe d'Huez or Holme moss...
What I find silly is the extreme segmentisation... going for a ride to chase a few half a mile long KoM, which are completely pointless. Each one to his own, but is it worth getting annoyed about these?left the forum March 20230 -
What I find silly is the extreme segmentisation... going for a ride to chase a few half a mile long KoM, which are completely pointless. Each one to his own, but is it worth getting annoyed about these?
Grand Tour stages are won and lost on 500m sprints.
In Quimper there are a few short steep climbs of 300 to 700m, about 6 to 10%. Even though the French have been slow to embrace Strava, these are quite hotly contested by several riders. Here's one; https://www.strava.com/segments/1617036
I can't TT for toffee, but I can do short explosive bursts quite well, so why not enjoy the fun?!0 -
Children aside, life is meaningless if you want to analyse things too deeply.[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630099#p19630099]steadyrollingman[/url] wrote:That's the sort of margin of error that can put you in the Top 10 or keep you outside the Top 50... So I'm beginning to think that most KoMs should be taken with a pinch of salt...
Now I just need to work out which duplicated rides I should delete so as not to drop down the leaderboards...
:roll: :roll:
Or come to the realisation that Strava segments are meaningless...The above may be fact, or fiction, I may be serious, I may be jesting.
I am not sure. You have no chance.Veronese68 wrote:PB is the most sensible person on here.0 -
[url=http://www.bikeradar.com/forums/viewtopic.php?p=19630860#p19630860]steadyrollingman[/url] wrote:which is effectively the same thing as setting KoM on a short Strava segment, bar all the dozens of variables...
it isn't... your effort is completely pointless and I already explained why in a previous post. A 1 minute long Strava segment on open roads is not something worth chasing, let alone going on about it because the rudimentary technology you have to record time gives unreproducible results.
If timing a 1 minute effort on the road was a meaningful enterprise, there would be half a mile time trials.
All I have seen similar is a "bicycle drag race" in a closed circuit, where max speed over a speed gun is the goal
I was never 'going on about' 1-minute long segments at all - but chasing those segs, despite their greater margin for error, is just as valid for the sprinters among us who might be lucky to grace the Top 50% of Box Hill etc.
And like someone already mentioned, if this tech, for all its faults, helps you ride more then it's not meaningless at all, quite the reverse. There are days when I get up and don't particularly feel like cycle commuting, but the ability to (fairly) accurately test myself against my own previous performances, and those of others, whether by using my Edge or Strava,is what drives me to put my shorts on. Before Strava, I'd probably have clutched at any straw to drive to work instead - some of us are driven by performance, not just the joy of pedalling. What's so wrong about that?Job: Job, n,. A frustratingly long period of time separating two shorter than usual training rides0 -
I did the same ride twice on strava and the first time it came out 23.1 miles at an average of 15.4mph and the second time it came out at 22.3 miles at an average of 15.4 despite being 4 minutes quicker second time round.hmmmmmm0
