4.24 Firmware... altitude and barometric fix

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rruff
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Joined: Wed Apr 23, 2008 10:48 am

4.24 Firmware... altitude and barometric fix

Post by rruff »

I'm curious about this because I've noticed as much as a 5% variation in the slope determination on a long climb that do frequently, where the altitude goes from ~7700ft to 10000ft. I wondered if it correlated to barometric pressure somehow, but never bothered to sort it out. Could anyone go into more detail on what has been changed? Does the initial altitude setting now effect the accuracy? Is the accuracy also improved on hilly (up and down) terrain?
Velocomp
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Re: 4.24 Firmware... altitude and barometric fix

Post by Velocomp »

Slope is determined from the accelerometer, not baro sensor, so the FW change should have no effect on slope measurement.

Also, initial altitude setting has no effect on any calculation; it is just an "offset" to the starting measurement of the baro sensor. It too will have no effect.

FW 424 does a better job of dynamically measuring and correcting minor variations in riding tilt, particularly as a consequence of up and down terrain. You should see improved accuracy.

It would be helpful if you could email a few ride files of the same route, with pre/post 424 FW.
John Hamann
rruff
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Re: 4.24 Firmware... altitude and barometric fix

Post by rruff »

But slope is adjusted by the altitude reading, so the barometric sensor does effect the slope. IIRC the update said that it improved the results if there was a change in barometric pressure or large changes in altitude... which I assumed meant that it does a better job of determining the correct altitude.

I'm not sure how the barometric altimeters work, but they must determine the altitude based on pressure and temperature. The change in altitude that corresponds to the measured change in pressure will vary depending on the starting point... so if you get the altitude wrong at the beginning you've introduced another source of error.

It will be awhile before I can do that climb again, but I can compare some other routes.
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lorduintah
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Re: 4.24 Firmware... altitude and barometric fix

Post by lorduintah »

Even the airplane rendition of altitude/barometer has to be adjusted for changes.

Tom
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