High HDOP values when flying IRIS

Are you guys also frequently seeing high HDOP values of over 2.0 and as a result IRIS failing to arm in GPS-assisted modes (Loiter and Auto)?

I'm hitting this problem in probably 8-9 out of 10 flights, but believe I have found the cause and a workaround: http://cloud-surfer.net/2014/09/12/high-hdop-values-when-flying-iris/

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  • I am still on 3.1.4. Don't know if that could be the difference. I have this problem occasionally especially if the Pixhawk and GPS haven't been powered up for a week or more. 

    Just like your describing. It'll sit there for like 10 minutes and not get below 2.5. When this happens I also notice that the telemetry  signal is reading low as in ~74% when they are only 10' apart. If I cycle power to the copter I have good HDOP within a minute. It happened yesterday once but it's been a few weeks.


  • What I find odd is my Iris never used to have any problems arming, and then one day it started refusing to arm.  It takes ~15 minutes for it to arm, like you said, almost every time. Did this HDOP vs PDOP problem come up because of an update? Thanks for the research into this! its good to know we can safely raise the 'HDOP' arm limit without fear of an actual gps connection problem.

  • Christian,

    I used to have this problem a lot until I put the mast on my Iris and got the GPS away from all that stuff. I have my arm failsafe set for 2.5 and even if the GPS hasn't been powered up for a week I still always get below 2.5 with 5 minutes. Once it's in the air I get anywhere between 1.9 and 1.2.


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