Replies to This Discussion

3D RoboticsPermalink Reply by Chris Anderson on March 28, 2012 at 9:03pm

Thanks for the update, Tridge. The compass changes in particular are a big help. Looking forward to seeing that in ArduCopter, too. 

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Permalink Reply by Gábor Zoltán on March 29, 2012 at 6:01am

Great news!

Manual level was the first on my wish list. :) 

THX! 

 

 

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Permalink Reply by Brad Smith on March 29, 2012 at 9:02am

good deal ,,, for me judging level is the hardest part : ) other than launching ,,,

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Permalink Reply by William Premerlani on March 29, 2012 at 12:02pm

Hi Tridge,

I am glad to hear that in flight magnetometer offset learning is now working well enough for you to release it. I enjoyed working with you on it.

If anyone is interested, the basics of the new algorithm are described here.

Best regards,

Bill Premerlani

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Permalink Reply by Veikko Vierola on March 29, 2012 at 4:47pm

Nice updates, thanks for them...

I was still hoping some kind of update for the altitude initialization too...

 

"Could it be possible to change the APM code so that the barometer would be calibrated last in the sequence, for example 45-60 seconds after power up. This way the GPS would have enough time to get satellites and steady position for the initial altimeter calibration? Or maybe after a reasonable VDOP value is achieved.."

Andrew, what is your opinion about it?

-Veikko-

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DeveloperPermalink Reply by Andrew Tridgell on March 29, 2012 at 6:40pm

Hi Veikko,

I agree that we could improve the altitude calibration. What I tend to do is use a ground station to force new calibration once the GPS has been locked for a while. That is really just a workaround though and you're right that we could do better without asking the user to use a ground station.

Perhaps something like this would work:

• get initial fix as we do now
• update the fix on each new GPS point, as long as the barometric altitude hasn't changed by more than 2m and the GPS ground speed has stayed below 0.5m/s.

The idea is to keep updating the home altitude until we actually start flying. Maybe use a 0.95 lowpass filter for the update?

I'm not sure using the VDOP or other value from the GPS will work well, but if you have some logs showing it does then we could look at that instead.

Cheers, Tridge

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DeveloperPermalink Reply by Andrew Tridgell on March 29, 2012 at 6:47pm

btw, if we do this, then we should probably also update the home latitude and longitude as well. We have occasionally seen logs where the initial GPS fix was awful (I've seen one where it was off by half a kilometre!), but it tends to fix itself quite quickly.

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Permalink Reply by Veikko Vierola on March 31, 2012 at 6:13am

I think maybe the first init should be done 30-60 seconds after power-up, perhaps update fixes during flight are not necessary.

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Permalink Reply by Tom in ON on March 29, 2012 at 5:30pm

Thank you Andrew and Bill!  It solved my previous compass problem and the rest of the parameters seem very steady as well.

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DeveloperPermalink Reply by Andrew Tridgell on March 29, 2012 at 6:40pm

good to hear! thanks for the feedback

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Permalink Reply by Brad Smith on March 29, 2012 at 5:30pm

is this only for the APM 2

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3D RoboticsPermalink Reply by Chris Anderson on March 29, 2012 at 5:37pm

No, it supports APM 1 equally well. 

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