Strava live segment for a non-uniform climb - how is position/time calculated?
Answered
Loving the Strava live segments feature of the Karoo. I have a question:
Let's say you have a PR of 30 min for a 5 mile climb with an unchanging grade (or a flat section of road). Then you come back and by going +1 mph faster (or whatever) beat that PR by 5 minutes (new time = 25:00). If the Karoo knows only the old PR time (and not minute by minute speed), it's easy to plot the old PR icon location vs current position. In this case the icon showing the old PR slides back (to the left) and stays behind you for the whole segment at a relatively constant widening gap.
Now lets say the segment is a 5 mile climb where the grade is 3% for the first 4 miles then kicks up to 9% for the last mile. Most of us would ride slower in that last mile. Let's say the rider is doing a pace that sets a new PR of 5 seconds faster for the climb (segment). How is the old PR position calculated and displayed? There are two possibilities that I can see:
1. The Karoo knows only the final time and average speed. It plots the rider's position relative to the PR icon such that in the first 4 miles of the climb the old PR icon is way behind (to the left) since the rider is moving faster than the total time or average speed for the old PR ride. This because the Karoo doesn't know that the old PR ride pace slowed during the last mile. Then in the last mile of the ride, the old PR icon would quickly slide back to the rider's position icon but in the end be slightly behind to the left.
2. The Karoo knows the exact old PR speed for every second of the ride and more accurately shows the positions of the current pace and old PR icons. In this case if the new PR is 5 seconds faster than the old PR, the old PR icon stays very closely behind the rider icon for the entire segment. This would be a more accurate depiction of the segment dynamics.
What are people seeing and how does this work?
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Good question. Wahoo used to do 1) for years - I believe they changed it, but I am not 100% certain. I contacted the Wahoo support 1-2 years ago and they said it was 1). I do hope Karoo has implemented 2) - on my ride today I definitely had the impression that they implemented 1) though :-/
Looking forward to an offical answer.
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Hi Bryan, In simpler terms, we only calculate the time, and the results are reviewed on Strava. All the results are finally uploaded and decided by Strava and the algorithm they use to decide the winners. We do not have any control over it. There are instances where people acheive KOM on the Karoo but after uploading to Strava the result changes.
I hope this brings some context to the situation.
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Hi Bryan I guess with two linked data points (elapsed time / elapsed distance) over the whole segment of carrot/PR/KOM and your live data Karoo can calculate and display if you are ahead / behind and by how much time all along the segment. It is therefore your hypothesis 2 which is valid, hopefully!
On the map while racing you see the live position of those past recorded data as (elapsed time / GPS position) can be lively displayed
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