Track recording - Speed jumps up and down

Sjoerd shared this problem 5 months ago
Solved

Hi, I have a problem with track recording on a bike in Locus Map Pro.


When uploading the recorded track to GPX Editor I see that on some parts (in this case the first half) of the course the speed jumps up and down. From 16 km/h to 60 km/h. My actual speed is around 28 km/h for that part. See gpxeditor.jpg and gpxeditor zoom.jpg.


When I upload the same track to Strava the speed jumps are a bit smaller, but still considerable. Maybe Strava smooth things out a bit. See Strava.jpg and Strava zoom.jpg.


When recording my ride with the Strava Android App itself this problem does not occur.


These are my settings for track recording: Locus track recording settings.png

Comments (16)

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Good day Sjoerd,

sorry to hear about such troubles. Interesting problem that I already saw reported from an user before.


May I ask you for an additional help with this? Best is if I'm able to simulate same issue on own device. In this case, I would need special record of your GPS. How to do it:

- open Locus >settings > GPS > Record NMEA > track recording

- start recording as usually


If issue happen during your ride, after you save a track, send me NMEA file ( you may attach it here as zip file) that will be stored in Locus/data/nmea directory. With this file, I may be able to simulate your movement and measure speed values. Hope it will be simple for you, thank you!

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Hello Menion,


Yes, I will do that. Thank you for the support so far!

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Hereby the ride of today. The zip file contains the NMEA and the GPX file.


In the GPX file the speed jumps up and down during the whole track.

In the NMEA file the data seems a lot better.

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Good day Sjoerd,

thanks for recorded NMEA message. I'm trying to use it to simulate your issue, unfortunately it looks like all data are correct and track recorded by Locus Map looks also fine.


You wrote that problem is only after export? And what about chart directly in Locus app? Also are you using latest Locus Map version for export to GPX file?

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Hi Menion,


Yes I always use the latest Locus version. The chart in Locus looks ok,


I looked again at the difference between the GPX file and the extracted NMEA file in GPX Editor.

In the NMEA file every recorded point is at precisely 1 second interval, in the GPX file it differs with every point. When the interval is less than 1 second the speed bumps occur.


For example:

GPX file

13:38:34.530 32,8km/h

13:38:35.147 68,7km/h

13:38:35.894 51,9km/h

13:38:36.918 31,3km/h


NMEA file

13:38:34 31,7km/h

13:38:35 31,3km/h

13:38:36 30,8km/h

13:38:37 30,7km/h


Maybe it has something to do with my settings for Track recording - parameters. I have an interval of both 2m and 1 second. See attachment.

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Good evening,

problem with NMEA messages as you may see, is that they do not contain milliseconds, so values are always rounded to same second value.

Seems that problem is that on your device, location from GPS receiver has some random delay till it gets into Locus.


I had made one small improvement now, so please check next version if it helps. Cannot promise it will, so we will see. If not and you will still have some patience with me, we should try to continue work on it.

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Ok thanks.


So you don't think it has anything to do with my settings?


Of course I have patience. Locus is a fantastic app with great support!

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Settings: you may set higher number of seconds in recording profile. This will definitely solve this issue because time error that happen here is always smaller then one second. So if you define 5 sec as minimal interval, speed values will match a lot better then now. On second side, it is only a workaround, not a real solution for this issue.


As I wrote, I made a change so give next Locus Map version a chance ( release is planned on Monday ) and you will see. If there will be a problem, set your time interval to higher value as a temporary solution. It should help.

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I'll leave the settings as they are for now and report what happens with the new version.

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Hi Menion,


Here is a ride with the new version of Locus.


Unfortunately it didn't help, there are still strange values in the files. I see in the GPX file that on some parts of the ride every point is recorded in whole seconds and other parts contain milliseconds.

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Today's ride.

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Good day Sjoerd,


thanks for a files. Unfortunately after export, there are always already partially modified data so I'm unable to see real reason of this issue.


I've prepared special Locus Map Free test version, so simply install it and try a short ride with it. After you close it, in Locus/logs will be file with some debug messages so please send me this log, thank you!


Version: http://nas.asamm.com:8080/share.cgi?ssid=0I0L62A

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Hello Menion, here are the files.

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Good day Sjoerd,

thank you for a log. I see that your GPS unit in device send to Locus values with really weird times. Locus has it's own logic and try to fix it anyway it has a side effect in your case.

Anyway I made an improvements so it should be solved in next Locus Map version. Let me know if there will be anymore troubles. Thank you!

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Hi Menion,

In the new version the data is a lot better.

I've tested my gps with other apps and there I get the same strange values. So indeed it's not only in Locus. Hope you didn't have to compromise Locus to suit my device.

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Hello,

perfect, glad to hear it, thank you! And no worry, this fix maybe helps to other users as well.

Thanks