Make GPS the default for accelerometer

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MacBandit
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Make GPS the default for accelerometer

Postby MacBandit » Sun May 19, 2013 7:47 am

Is there a way to make the GPS calculation the default for accelerometer calculations? Using the iPhone doesn't work well on a motorcycled since the bike is leaned over in a corner and not flat like in a car.


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Harry
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Re: Make GPS the default for accelerometer

Postby Harry » Mon May 20, 2013 7:29 am

That is not possible currently. I'm working on a feature to both record lat acceleration and lean angle on motorcycles. Once it is available (v18/19), you will hopefully have no need for this calculation any more :-)

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MacBandit
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Re: Make GPS the default for accelerometer

Postby MacBandit » Mon May 20, 2013 5:42 pm

That would be awesome. Thank you very much.

I have another question.

I'm trying different lines at the track I'm riding and am trying to relate those to the times I'm getting. The app I use to use on android would show my exact lines in respect to the track map. So you would have the track map laid out like a road and the line I was taking within the boundaries of that road. Is that function somewhere in this program?


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Harry
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Re: Make GPS the default for accelerometer

Postby Harry » Mon May 20, 2013 6:30 pm

Please export your laps to .kml and watch in Google Earth. In my experience, GPS accuracy needs to be really high to derive reasonable information from plot comparison.

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Re: Make GPS the default for accelerometer

Postby MacBandit » Mon May 20, 2013 6:35 pm

I'm using the XGPS150 with my iPhone. I hope that would be good enough since I was able to do this before with just the Android phone though the tracking frequency made the plotting very coarse but it was still distinguishable and it was visible on the phone app without exporting.

The reason this is super useful in phone is that I can check it quickly between sessions rather then waiting until I get home to use a computer.

Thank you again for your quick replies and great app.


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Re: Make GPS the default for accelerometer

Postby gplracerx » Thu May 30, 2013 9:30 pm

Harry wrote:That is not possible currently. I'm working on a feature to both record lat acceleration and lean angle on motorcycles. Once it is available (v18/19), you will hopefully have no need for this calculation any more :-)

Harry


You need pitch as well to correct for elevation change. To have any hope of doing that properly, you need vertical as well as horizontal velocity from the GPS, even if the vertical velocity will never be as precise as the horizontal velocity by the nature of GPS. You should also be calculating horizontal acceleration from the GPS velocity and rate of heading change rather than position. Calculating vertical velocity from the altitude reading is really, really noisy. The VBOX Sport is supposed to give vertical velocity, but it isn't working right now. And that's been acknowledged by RL, it's not just a problem with my box.

I've looked at the vbo file from the SD card in my VBOX Sport, and I see changes in velocity when there is no change in position because of insufficient resolution of the position. Interestingly enough, you also get lateral and lineal acceleration, although right now the column labels are reversed. Surprisingly, when you open the vbo file in Circuit Tools, it recalculates the accelerations.


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Re: Make GPS the default for accelerometer

Postby Harry » Thu May 30, 2013 10:14 pm

When *calculating* acceleration you will apply different calculations in real time and in an analytics tool like CT. In real time you cannot look ahead and use this fixes ahead to calculate acceleration. In case you do it after the fact, you will use fixes surrounding the position acceleration is calculated for, and apply additional smoothing like a Kalman filter. I assume acceleration calculated by CT is a better approximation of reality than that written in realtime by the VBOX. LapTimer's acceleration calculation is not too sophisticated today, but it makes exactly that differentiation.

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Re: Make GPS the default for accelerometer

Postby MacBandit » Fri Jun 26, 2015 7:13 am

I know this is an old topic now but with v19 we now have the calibration option for motorcycle but I'm still having to use GPS to get any sort of guess at g-force calculations.


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Re: Make GPS the default for accelerometer

Postby Harry » Fri Jun 26, 2015 7:19 am

Please check the Quick Reference illustration #4 to see the mounting position required to make motorbike acceleration measurements work. Any other position requires you to use LapTimer's know individual calibration. Especially lean angle measurements (part of 19) are sensible with respect to mounting, so take care to use the tilt shown. You can calibrate your position by selecting Acceleration View. For correct mounting, you should see 0 acceleration when standing still and upright.

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Re: Make GPS the default for accelerometer

Postby MacBandit » Sat Jun 27, 2015 9:44 pm

I'm not sure what position the quick reference is showing. If it's flat laying on the tank or if it's vertical. I actually had to take a screen shot to even get that much from it. The slideshow goes by way too fast to try to figure out what it's describing.

Here's what I currently have setup. The optrix mount on the left bar.
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