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How does Edge 530 calculate ahead/behind times for Strava Live Segments?

Cankut ESKİN
over 4 years ago

Hi,

Device: Edge 530

Software Version: 7.10.0.0

Case: Testing "Strava Live Segments" feature on a ~1.4km climb with average gradient of 7.9% (a goal finish time of 7 minutes is set and synced to the device)

Segment Link: https://www.strava.com/segments/3840095

Activity Link: https://www.strava.com/activities/5175936601

The climb starts with gradients ranging 6%-9% until half way and goes up to 9%-12% on the last half.

I repeated the climb 5 times and I've noticed that, for the first half of the climb, time ahead/behind shows me that I'm ahead of my goal time by 5-10 seconds.

And for the second half of the climb, the 5-10 seconds advantage starts to drop towards zero, and I start to push harder to keep the time advantage.

If I were to keep my first half effort for the second half, maybe it would tell me that I was behind of my goal or even out at the end.

This ahead/behind time calculation seems a bit confusing to me because I was very confident that since I'm +10 seconds ahead for the first half, I could go easier for the rest of the climb.

My guess is; 

Device calculates an average speed for the whole climb to reach the goal and whenever you ride slower than that pace, it starts to drop your ahead time and vice versa.

A better approach could be taking the changing gradients into account and processing in an algorithmic way.

A few questions for fellow Garmin users:

  • How do you pace your outdoor interval workouts?
  • Do you use Live Segments for interval workouts too?

Thanks in advance.

  • 0 over 4 years ago

    I think the actual position of the rider you are being compared to is recorded at various time points and the unit works out how far ahead/behind you are of that person based on your speed.

    So, you could well be ahead during the first half of the segment in question but you are then slower than the leader during the second half which is why your lead evaporates then.

    If you do a comparison of your time and the leader's time in Strava you would probably see something similar.

  • 0 over 4 years ago in reply to Wongataa

    Thank you for your reply. In my case, there is no other rider, I just set a time goal of 7 minutes and go.

    If I had chosen a PR or some other athletes time to race against, theoretically, yes, the device can use location data to calculate better estimates.

    Yet we're not sure since it's not documented anywhere or someone tested and verified Live Segments works as you have explained above.

  • 0 over 4 years ago in reply to Cankut ESKİN

    I have the same issue as Cankut. Can Garmin Admin revert with a response pls?

  • 0 over 4 years ago in reply to cdhargraves

    Pretty sure it's on average speed, that's my experience. Don't forget that live segments is really a strava thing, so i don't think garmin are going to spend too much time on it. I think Garmin connect has connections and segments features, but nobody uses them, because strava is so popular.

    MB

  • 0 over 4 years ago in reply to meltonboy

    it's based on average speed of segment so not relevant if profile of climb is not regular ...

  • 0 over 4 years ago

    Thanks for the responses. 

    So live segments is useless if the gradient changes during a segment. It looks as though this has been an issue for years.

    Segments are being recorded by the second (demonstrated by the Compare functionality on the Strava website) so I don't see this is a Strava issue. The data is there ready to be used. Its really up to Garmin to access that data and present onto their units in a way which enhances the user experience - isn't it?

    True live segment (similar to compare functionality) data in real time would be awesome. Do any head units offer this? I would transition immediately if it were available. 

  • 0 over 4 years ago in reply to cdhargraves

    Well the data is certainly there, but obviously it take more processing power to integrate the split second activity data for every entry on every leader board than just the times. With modern servers, maybe that's no big deal, but it is more work.

    And just because it's on strava doesn't mean Garmin has access to it. If strava just share the leader board times because they haven't processed the activity data in that way, or they have but don't wish to share, there's not much Garmin can do. This is just supposition on my part, but it certainly doesn't feel like Garmin has all the data but not using it. But i could be wrong!

    I think you've raised a classic example of something that's important to you, but not high on developers to-do list. Maybe because it isn't that important to many other users. I have the same thing with the navigation bugs i'm experiencing with the unit. Right now i wouldn't buy another 530, if i needed a new one, because navigation is a key feature for me, personally.

    MB

  • 0 over 4 years ago in reply to cdhargraves

    I don't know about Strava segments but Garmin segments Have location and distance information every 3-6 seconds (in one of mine I looked at) so can compensate for changes in speed through the segment.

  • 0 over 4 years ago in reply to Wongataa

    It should be comparing times at every data point. So if the original was recorded using 1 second recording then it should be checking and updating the time every second.  

  • 0 over 4 years ago in reply to aweatherall

    thanks .  To clarify do you mean on Garmin segments or Strava segments?

    thanks the response