BUG: Strava Live Segments doesn't work as expected
Answered
This is not related to the new presentation of SLS as released last week. I've suspected something was not quite right before that but now I have some concrete data points to present as I suspect the implementation does not work as expected.
Just came back from a steady evening ride. A local loop - on roads - roughly 20 km or so. I have a few local segments synced on the Karoo, just in case I fancy pushing myself on any of them and I wanted to see what the new drawer presentation of SLS looked like.
This evening, I was following my progress on one particular segment and was led to believe - by the Karoo - that I achieved a new PR with a time of exactly 00:05:00. Yay me. The Karoo even told me I had achieved a new PR on that segment (although it was difficult to know which segment it was referring to, exactly, since a few segments all finish at that point and I could not see the name of the segment anywhere). Great, I thought. At least one new PR in the bag this evening (and there was only one PR on my ride this evening). So I continued home and uploaded the ride from the Karoo as soon as I got back.
Now this is where it gets a bit weird...
When I looked at my data on the Strava app, I was expecting to see a new PR for the segment the Karoo told me that I had achieved a new PR on (you would too, right?). Instead, what I saw was a new PR for a completely different segment that finished a few km earlier in the ride and was nowhere near the finish line of the segment that the Karoo thought I had achieved a new PR on. Instead, the segment that the Karoo told me I had achieved a new PR on, actually took me 23 seconds longer this evening than my PR (00:04:37) on Strava. See screen capture from Strava:
Why is the Karoo telling me I've achieved a new PR for that segment when I was 23 seconds slower than my previous PR on that same segment?
I'm pretty sure this is not the first time this has happened but I feel as though I have more concrete data points for you to investigate this time.
Like I said earlier, I don't believe this has anything to do with the new presentation of SLS; this problem existed way before that.
Thoughts, anyone?
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I’ve had some odd data come up also - PR’s showing up even as I can see I’m trailing by a few seconds or more as I’m approaching the end. I’ve also noted that sometimes I see my progression in relationship to both my PR and a Wolf, whereas other instances, it’s shown only in relationship to the Wolf time.
I don’t think once you start a SLS that you ever have a chance of seeing the segment name again - an issue that needs to be addressed especially when there is overlapping segments.
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I had similiar issue with Garmin and Wahoo with both showing me that I beat my PR, but not according to Strava. I don't remember the error margin unfortunately.
Maybe it has something to do with different calculations from hardware (bike computer) and then software (Strava algorithm)?
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Hello all!
There are likely a few things going on here. Regarding SLS, there are more enhancements coming there including more clarity around names when you have overlapping segments. We are working on a way to have the segment names available so that close or overlapping segments aren't as confusing. You will see that in an upcoming update.
Not to say this is your issue, Steve, but another thing that can cause similar situations (probably the root of what Ornaled experienced) is that Strava uses different algorithms than the head unit manufacturers and it doesn't always match up - it can cause differences and even debated PRs, KOMs, etc. They have an article for every head unit manufacturer providing an explanation/disclaimer of why that can happen.
Steve - I can't speak to why you received a late notification for an earlier segment or an incorrect notification for the one you were completing - it is hard to say which scenario is the case here. I will keep watching for more instances like this to hand over to our software team to investigate. Please let us know if you have additional examples we can review.
Thanks!
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Thanks for your thoughts on this, Jami.
Displaying names of segments is a must have, really. The only time you see the name of the segment is in the upcoming segment notification and then you never see it again.
In the example I gave above, I'm confident it was an incorrect notification rather than a late notification because the time of 05:00 was (incorrectly) provided as my new PR time for that segment. The time of the segment I did achieve a new PR on was slightly longer - with a steeper gradient - and timed at 06:20. That is how I know it was an incorrect notification rather than a late notification.
From Strava:
Why is my segment time different after I upload it then it was on my Karoo?
Karoo devices use a different algorithm for determining when an athlete starts and finishes a segment than Strava uses, which can affect the elapsed time reported for the segment. To ensure consistency between athletes, the times shown on the Karoo during an activity are preliminary, and the times shown on Strava after uploading are final.
Ultimately, I guess you can't rely on the SLS notifications on the Karoo; It's only when your data gets into Strava that you see the real picture.
I don't really understand why this is so hard to get right. In simple terms, you're basically measuring the total time spent between two GPS waypoints; the start and the end point of a segment. It should really be no more complicated than that. Other data (speed and power, for example) can be derived from the time and distance. When you sync segments with Strava, there's various data points you should be pulling down:
- KOM/QOM time
- Carrot time
- Wolf time
- PR time
- MR time
- RB time
If a segment is completed in a time that is less than one of those values (take PR for example), then notify the rider that they have achieved a new PR/KOM or whatever.
In my example above, my PR on a given segment is 04:37. If I spend 05:00 on that segment then that is clearly not a new PR is it? If I spend 04:36 on that segment then I will take that as a new PR. If the Karoo has my PR time synced, why would it then tell me I've achieved a new PR when the time taken was 23 seconds greater (slower) than my PR?
I appreciate that Strava may apply different algorithms to the head unit manufacturers, but Strava Live Segments should just be a simple measurement of time between two GPS waypoints. Or am I missing something here?
I'm kind of confused by how all this works but I have a mental model of how it should work in my head. The current implementation does not match my mental model and I don't have any confidence that it works correctly.
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I currently ride with a Garmin watch and the Karoo2 at the same time. During a segment there are often significant differences between the time ahead/behind a PR or KOM, but by the end of the segment it all seems to work out ok. I suspect this is what Jami is referring to when he says that each head unit manufacturer deals with the calculations in their own way. And I get that, some attempt to give a like for like update versus a previous ride taking into account different speeds at different time, some just average speed across the segment and display progress against that average
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