Custom Data Tracks

by old_man_biking

Downloads: 1,790 (5) • Reviews: 0

Version:

3.0.5980

Updated:

May 15, 2016

specified cast is not valid

specified cast is not valid

Postby Doug Smith » Sat Oct 29, 2016 12:27 pm

Hi,
I'm trying to use Custom Data Tracks to calculate the power from my bike trainer (for some reason the Trainer Power plugin by mechgt is not calculating correct values for me). I think I did everything correct, and when I look at the custom data track, it is empty. That's when I see this error "specified cast is not valid".

Any idea what is happening?
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customTrack1.PNG
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Doug Smith
 
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Re: specified cast is not valid

Postby old_man_biking » Sun Oct 30, 2016 4:41 am

Please post your exact formula (as text not as screenshot) and attach a zipped .FIT file of this activity.
I'll have a look, then.
Cheers,
OMB
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Re: specified cast is not valid

Postby Doug Smith » Sun Oct 30, 2016 10:06 pm

Hi, thanks
I think I know part of the problem now. I'm importing my workout from my Suunto watch. The workout is a bike trainer workout. When I import the workout, ST asks me if I want to calculate distance based on GPS. I say "no" because I'm getting speed/distance from the bike pod/wheel sensor. The workout looks fine after import, the speed is showing correctly. When I exit ST and then open it again, the workout no longer has correct speed. It's as if all the speed data has been erased.

Looking at the fitlog file I've attached (DougST.fitlog), it doesn't contain any speed information. I have no idea why ST won't save the speed data from my imports.

I'm also including the fitlog file for the same workout after I've used the "Trainer Power" plugin. This fitlog file holds more info obviously, although for some reason the trainer power plugin is not calculating the power correctly.

Here is the calculated formula copy and pasted: Math.Pow({DataPoint.Speed},3)*0.019168+{DataPoint.Speed}*5.2449
Attachments
DougST.zip
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Doug Smith
 
Posts: 11
Joined: Sun Oct 18, 2015 8:15 pm

Re: specified cast is not valid

Postby old_man_biking » Mon Oct 31, 2016 11:15 am

Sorry, but the two .FITLOG files, which you've attached only contain temperature information, no speed, nothing - as you said yourself.
Please try and fix this issue first, before you try to use non-existing speed information in a calculation formula. I'll glad to help if there will be an issue with CDT plugin then.

Cheers,
OMB
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Re: specified cast is not valid

Postby Doug Smith » Wed Nov 02, 2016 12:07 am

Here are two new .fitlog files with more data. I have the import working better by importing the suunto file instead of directly from the watch. It looks like the data from my Suunto contains time and distance, and ST calculates speed from this. The formula I'm using for Custom Data Tracks is: Math.Pow(({DataPoint.Speed}*3.6*.62),3)*0.019168+{DataPoint.Speed}*5.2449*.621*3.6

I don't quite get the difference between these two custom data tracks. For the "good" one, a speed of around 30 km/h gives a power of around 210 W. This is what I expect. But for the "not as good" custom data track fitlog, a speed of 30 km/h is giving a power of 300 W.

Is this because of the quality of the data from the Suunto? That the calculated speed jumps around too much, which gives bad calculated power?

thanks
Attachments
DougData.zip
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Doug Smith
 
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