Altitude GPS correction

Posted by Arthur Guy on November 21, 2012 at 5:42am

Hello,

I am just getting started with an arducopter controlled quadcopter and I am having some problems with altitude readings.

When I try switching into altitude hold mode the quadcopter drops to ground level and then when I switch out it returns to its previous height. I would have thought what ever the readings coming from the barometer or sonar sensor the GPS altitude reading wouldn't allow this much movement.

Can someone let me know how the GPS altitude readings affect the overall altitude reading?

Thanks

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Replies

  • Alexey Kozin November 21, 2012 at 9:52am

    in arducopter without sonar, with default settings gps not used

    accel not used  too

    only baro have effect to altitude control

    my quaid (apm2 / ac 2.8.1) holding less than 1 meter

    I use  double vibration-damping for controller and a sealed box with a tube up to take a sample from the pressure above the swirling propellers. 

     

    (box is used for protection when flying in the rain,
    ESC sealed with hot melt    )

  • Randy Brazeau November 21, 2012 at 6:23am

    I would be interested in how ALT Hold works also.

    Are the GPS, Baro and Sonar all used for alt hold?

    I just started testing Alt Hold the other day. It was an altitude of about 10 - 15 meters and I would say it was holding about 3 - 5 meters. I would  fly around (I'm just learning)...and it appears to be working but at the end of my flight it was touching the ground. A slow drop in altitude.

    I'm playing with the PID's to get a feel.

     

    Randy

  • Arthur Guy November 21, 2012 at 6:22am
    @Will Snodgrass
    I tried with and without the sonar and it behaved the same both times, it was over solid ground so the sonar sensor seemed to be returning alright data.
    I have covered the barometer but perhaps not well enough.

    Does the GPS have any corrective effect on the altitude readings?
  • Will Snodgrass November 21, 2012 at 6:09am

    Are you using a sonar sensor? Also is your barometer sensor covered up with something so that the wind does not affect altitude readings? It's possible your quad may be thinking it's much higher then it actually is.

  • Alexey Kozin November 21, 2012 at 5:49am

    even the best GPS units makes an error of 3-5 meters in the ground plane can make an error of 20 meters in altitude. GPS makes sense to consider the altitude where the barometer may not be accurate - more than a few miles

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