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Wrong speed displayed on track chart plot

Svitozar shared this problem 6 years ago
Closed

Lap interval average speed is higher than even the highest speed on chart for given parts of track (which I find not correct)


Jogging track was recorded with 8m&2sec interval, record only when moving. No pauses, no sharp turns

Replies (2)

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Good day Svitozar,

may you please export your track into GPX file and share it with me here?

I'm anyway worried that for now, I won't have any solution on this. Chart is highly optimized and display filtered values. Lap intervals are computed from un-optimized vales so average speeds etc. may be a little higher. Logical solution should be to compute all necessary tasks on already optimized values, which is not now done.

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To my mind, the velocity difference (7 vs 10 kmph) looks too large to be caused by location errors. Don't know your filtering principle, but there were large straight segments on my path and i don't see any significant transverse location noise (longitudinal should cancel out).

Average speed calculated on paper looks consistent to the lap values, therefore performing filtering would only spoil the correct data.


Maybe you should consider reviewing your filtering algorithm? Probably it is too agressive =)


Concerning the rest - great app. Thanks for your job!

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Good day Svitozar,

this is really interesting. I've imported your GPX data and this is what I get ( see screenshot )

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When you record track directly in Locus Map, speed value is part of received coordinates, so Locus Map use it. When you anyway export data to GPX value, these speed values are not included. So during import, Locus Map computes speed values from coordinates ( divided by time difference ).

So for me it looks like coordinates are correct, but speed reported by Android GPS is not perfect. Values in "Laps" tab are also computed from raw coordinates, so this fit to my explanation.

This is really complicated problem. From my experience, usually worst are "coordinates" then "speed" reported by GPS system. So it does not sound to me like a good idea to completely discard these speed values and always use speed from coordinates.

I"m sorry, currently I have no instant solution. This whole system is quite sensitive and minor changes here may cause troubles on different places.

Thank you for understanding.

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