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Compass Error vs K-index vs Satellites

Discussion in 'Pro/Adv Discussion' started by jayhkr, Oct 22, 2015.

  1. jayhkr

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    Hey everyone! Hope everyone is flying well and safe! Have a question about K-index, satellites and compass reliability. I've learned to check the K-index before each flight at www.uavforecast.com and today it showed it to be a solid 2 all day. Low wind, gusts MAYBE to 15mph, partly cloudy, upper 70's, just about perfect! Took the bird out to my favorite spot and had a great first battery. Been flying my waypoint missions everweek so I can capture the ever changing foliage in my area so I can make a (hopefully) cool video come time spring. No issues on my first battery, swapped out to the 2nd battery and just flew around as normal when I get the red "compass error" message and the system automatically switches to ATTI mode. Of course no one likes it when we're out of GPS signal so I brought her in and struggled just a tiny bit getting her down, nothing big. My question is what would cause it? Checked the website on my phone again and K-index still showed 2. I'm not one to take a chance all the time so I didn't go back up. Made a phone call within the park I was flying and had a brief connection loss on my phone where the other person couldn't hear me (I heard them just fine though). So could there had been some sort of cosmo interference for a short time? Was it something outside the "nature of things", meaning a technical issue? During the whole flight back in ATTI mode I still showed 15 satellites strong so I couldn't figure out why it lost gps/compass capabilities.

    Fast forward to this evening, I wanted to take the bird up for the sunset as I have yet to capture a REALLY good sunset. ZERO wind, still partly cloudy, and mid to lower 70's still, again PERFECT! K-index again showed 2. Took her up and was going great for 5 or so minutes when I again lost GPS mode, auto switched to ATTI but this time I noticed a TON of sway. To the point that my heart escalated to OMG mode! Still got her down safe and sound (this is why I practiced ATTI flying long ago!). There were a few people where I was with their dogs and after I landed I struck up a conversation and started my "information speil" or "Teaching Mode" if you will to them when they found out I was flying a "drone". Great people, super curious and excited. They of course wanted to see it go up again. Checked the K-index and still showed 2, switched batteries and wanted to show them the automation flying of my waypoints, plus the lighting was perfect to get the trees/sunset. During the entire waypoint mission not one issue. Zero, Zilch, Nadda! So someone tell me what's going on here? First time out was around 1430 CST, and the second time was around 1800 CST. Video and Healthydrones.com log below. Thanks everyone for reading and helping.



    HealthyDrones.com - Innovative flight data analysis that matters
     
  2. Meta4

    Meta4 Moderator
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    Sounds like some temporary glitches. I can't shed much light on this apart from saying that it had nothing to do with the K-index.
    Poor quality mobile phone calls are a common occurrence and yours was almost certainly an unrelated coincidence.
    So far there's no evidence that high K-index has affected any Phantom flights and the whole K-index thing is believed by many to be over-hyped.
    If the K-index was to go very high, the effect on GPS would be to make the GPS error a little larger but this still shouldn't have any serious impact on flying.

    Your first incident was compass error. This indicates that the Phantom was receiving compass data that was outside the range of normal values.
    The Phantom switched to atti mode to eliminate conflict between bad compass readings and GPS.
    You don't mention the compass for the second incident so I'm not sure if it was the same cause or a separate loss of GPS.

    I'd want to look at the compass sensor values and possibly give the Phantom a good compass calibration if they looked wrong.
     
  3. jayhkr

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    Sorry, yes the second incident, the one I posted the video on, I also received a compass error, but this time the bird had the very noticeable sway. I always look at all values prior to takeoff and compass values were at 1489-1493.
     
  4. ianwood

    ianwood Taco Wrangler
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  5. flyNfrank

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    Why would you even consider not calibrating the compass after being fortunate enough to land without incident? I'm not saying calibrating was the fix, but in my opinion it should not have been flown until a compass calibration was done. It would be good to know how the sensor readings were displaying even while staged on the take-off area.

    At any rate, the best thing you did in this situation is sharing your experience here on the forum. There is a lot of people that lurk and never create an account, but the point is there are many out there that has probably had a similar situation they can now compare with yours.
     
  6. jayhkr

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    Why would I calibrate if my sensor readings all showed within spec? No reason to calibrate if what was on my screen in between what is stated as normal. But alas, tomorrow I will recalibrate. Thank you for the feedback everyone!
     
  7. flyNfrank

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    I generally steer away from this subject because most want to disagree to a point of arguing.

    Hopefully my question here will make some sense. When you looked at your sensor reading, was it preformed live, in flight, and during the moment of when the error message displayed? Of course if the readout was after landing and after the aircraft had become heat soaked, the readout would no good for what you were wanting to know. I have mentioned this several times, I calibrate after installing the 1st battery.
     
  8. reboot81

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    If having compass trouble it's best to try and eliminate all sources of error. Such as a bad calibration.

    Why? Here's a therory of mine, please correct me folks if I'm wrong:
    So if compass is skewed, but your'e on a location with a strong electromagnetic field it could trick fool you with an strange compass value, even one close to 1500! It's the compass value up in the air that's relevant, not the one when sitting/close to the gound.
     
  9. jayhkr

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    No, I didn't check the value while I had the error. At that point I was just trying to keep the bird from floating away on me. However I see your point. It's just odd that if a pilot is to keep his eyes on the target at all times, and does everything properly during preflight, how these things happen. I will recalibrate it today and see if that changes anything. Thank you everyone.


    Oh, can the ground electromagnetic fields change over time? I ask because I never had this issue in the beginning. Fly at this spot all the time.