Big fluctuations in gradient in GPX rides

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jaricketts
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Big fluctuations in gradient in GPX rides

Post by jaricketts » Tue Jan 15, 2019 12:24 pm

Hello, Is anyone else experiencing big fluctuations in gradient on GPX rides. I have always smoothed the gradient in rides plotted in RidewithGPS in 3Droutebuilder before uploading into the TAcx app. Before using the app, in TTS4, it worked fine with smooth rise and fall on climbs with easy fluctuations in gradient and steady pedalling. As an example, on my latest ride I got a max gradient in 3Droutebuilder of 6% but when I uploaded it into the Tacx app the max gradient was 13%, on a climb that went from 2% to 13% in the space of a few pedal strokes and then back to 6% again. Any comments or suggestions as to how to eradicate these large fluctuation would be gratefully received.

mcorn
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Re: Big fluctuations in gradient in GPX rides

Post by mcorn » Tue Jan 15, 2019 4:50 pm

jaricketts wrote:
Tue Jan 15, 2019 12:24 pm
Hello, Is anyone else experiencing big fluctuations in gradient on GPX rides. I have always smoothed the gradient in rides plotted in RidewithGPS in 3Droutebuilder before uploading into the TAcx app. Before using the app, in TTS4, it worked fine with smooth rise and fall on climbs with easy fluctuations in gradient and steady pedalling. As an example, on my latest ride I got a max gradient in 3Droutebuilder of 6% but when I uploaded it into the Tacx app the max gradient was 13%, on a climb that went from 2% to 13% in the space of a few pedal strokes and then back to 6% again. Any comments or suggestions as to how to eradicate these large fluctuation would be gratefully received.
There is something very odd going on here. I don't see how a ride that you smoothed with 3DRouterbuilder to a maximum 6% slope could have a maximum of 13% in TDA. TDA does not add slope in my experience. I have found importing after using 3DRoutbuilder works fine. Are you 100% confident that you are using the smoothed course when you import to TDA? I would inspect the file from 3DRouterbuilder in another program just to be sure it has been smoothed.

jaricketts
Posts: 27
Joined: Fri Feb 01, 2013 12:00 pm

Re: Big fluctuations in gradient in GPX rides

Post by jaricketts » Thu Jan 17, 2019 2:36 pm

Thanks for your reply. The reason I ask is I had no problem at all with the gradient smoothing via 3D routebuilder in TTS4, but I am getting this problem with the App. The gradient does change as a result of the smoothing changes in 3Droutebuilder as I can see the elevations change in the line above the numeric data and the data itself changes. I still have access to TTS4 and the gradient profile when I use it is in line with what I would expect from a file that has been processed through 3D routebuilder. Curious.

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Re: Big fluctuations in gradient in GPX rides

Post by mcorn » Thu Jan 17, 2019 4:24 pm

jaricketts wrote:
Thu Jan 17, 2019 2:36 pm
Thanks for your reply. The reason I ask is I had no problem at all with the gradient smoothing via 3D routebuilder in TTS4, but I am getting this problem with the App. The gradient does change as a result of the smoothing changes in 3Droutebuilder as I can see the elevations change in the line above the numeric data and the data itself changes. I still have access to TTS4 and the gradient profile when I use it is in line with what I would expect from a file that has been processed through 3D routebuilder. Curious.
It's a mystery to me. I just tried importing one of my 85 mile courses that I captured while riding on a bike. I first imported the raw version and then I smoothed it with 3D Route Builder and imported it. In both cases, I imported using the low TDA smoothing setting. It appears to work fine with the smoothed version the same as when it left 3D Route Builder.

Are you using the paid version of 3D Route Builder (3D Route Builder Plus). As I recall, with the free version, you cannot directly save smoothed courses - you have to copy all the data out of the table and paste it into a new GPX file outside the program.

jaricketts
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Joined: Fri Feb 01, 2013 12:00 pm

Re: Big fluctuations in gradient in GPX rides

Post by jaricketts » Thu Jan 17, 2019 7:34 pm

Thanks Mcorn, Yes I'm using the paid version of 3D routebuilder and the "save as" rather than the "export as" option. I haven't tried any changes to the TDA settings and will try that tomorrow and report back

jaricketts
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Re: Big fluctuations in gradient in GPX rides

Post by jaricketts » Mon Jan 21, 2019 11:54 am

Well that was a surprise..... and a bit counter-intuitive, but by using the lowest setting in uploading my rides to TDA over the past few days the gradient changes appear to be less extreme and more like what I would have expected with TTS4. Thanks for the advice Mcorn, I'll continue to use this setting in future.

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Re: Big fluctuations in gradient in GPX rides

Post by Tacx Video Production » Mon Jan 21, 2019 12:26 pm

jaricketts wrote:
Mon Jan 21, 2019 11:54 am
Well that was a surprise..... and a bit counter-intuitive, but by using the lowest setting in uploading my rides to TDA over the past few days the gradient changes appear to be less extreme and more like what I would have expected with TTS4. Thanks for the advice Mcorn, I'll continue to use this setting in future.
I think the higher settings ignore the alt data & probably use landsat data, you want to use the one thats recommended with Barometric data like Mike said & you have discovered, think it still smooths it a bit but I tested it with the data used in the RLVs thats all grade checked with the films & it stays close enough.

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Re: Big fluctuations in gradient in GPX rides

Post by mcorn » Mon Jan 21, 2019 6:40 pm

Tacx Video Production wrote:
Mon Jan 21, 2019 12:26 pm

I think the higher settings ignore the alt data & probably use landsat data, you want to use the one thats recommended with Barometric data like Mike said & you have discovered, think it still smooths it a bit but I tested it with the data used in the RLVs thats all grade checked with the films & it stays close enough.
I still think he is making some kind of error with 3D Route Builder. In my own ride that I have smoothed with 3D Route Builder, TDA shows 9% maximum slope on low, 8% on normal, and 8.4% on mobile. If I don't smooth this ride with 3D and import at low, it is 11.3% maximum. I am at my desk and not on the PC where I use TDA, so I was not able to more carefully inspect the profiles of the various files, but I suspect that the TDA functions (as well as 3d) are working the way they are supposed.

mcorn
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Re: Big fluctuations in gradient in GPX rides

Post by mcorn » Mon Jan 21, 2019 6:44 pm

jaricketts wrote:
Mon Jan 21, 2019 11:54 am
Well that was a surprise..... and a bit counter-intuitive, but by using the lowest setting in uploading my rides to TDA over the past few days the gradient changes appear to be less extreme and more like what I would have expected with TTS4. Thanks for the advice Mcorn, I'll continue to use this setting in future.
It still sound like something is not right to be. The higher TDA import settings should do more smoothing than the low.

Here is a link to a free online GPX smoother that is easy to use. Why don't you try it as an experiment and compare with your 3D results:

https://www.lunicus.org/tacx/GPXsmoother.htm

mcorn
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Re: Big fluctuations in gradient in GPX rides

Post by mcorn » Tue Jan 22, 2019 2:35 am

Did a GPS ride today used one of my outside rides captured with a GPS unit. I smoothed it in 3D Route Builder and imported into TDA with minimal additional smoothing. The ride was quite smooth and did not have any sudden slope changes. So, from everything I can determine, both TDA and 3D Route Builder are working fine.

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