Mikrokopter error 21 - GPS Fix Lost *oddity*

Discussion in 'Electronics' started by Derek Cooper, Sep 6, 2015.

  1. Derek Cooper

    Derek Cooper Active Member

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    Hey,

    Today we had "One of those flights," but of course my pilot Wesley was able to save the drone and bring it down safely. He baffles me almost daily with his skill.

    Drone reported error 21 - GPS Fix Lost. Logs confirm it, but what is odd is the logs show 7 satellites the entire time; whereas the error isn't supposed to occur until you have fewer than 4 satellites.

    Any ideas?

    Derek
     
  2. Gary Haynes

    Gary Haynes Administrator
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    While you have 7 it's possible that the ones that the MK was trying use for the fix were low to the horizon and while it 'sees' the sats wasn't getting a reliable data stream. Obstructions around the flight area combined with low horizon sats might do it.

    Also depending on when you were flying the GPS signal may not have been good. K index was at a level 4 about 6 hours ago.
     
  3. Derek Cooper

    Derek Cooper Active Member

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    Thanks Gary - always terrific feedback from you that is greatly appreciated.

    Why would the drone behave erratically when it loses those GPS fix? Wes did have the drone in GPS hold at the time. Would that suffice?

    Lastly - what do you recommend as the base website to monitor the K index?
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Derek: I suspect Gary's off-line (it's a long weekend here in the USA).
    For KpIndex:

    uavforecast.com (good for weather and KpIndex). The guy that runs it could do with a modest donation as it's the most useful site in terms of collating all the data.

    For just Kp Index:
    http://www.swpc.noaa.gov/products/wing-kp

    I have an app that shows me the current time in UTC to make it easier to interpret the forecast.

    If the GPS system loses lock, then the GPS's idea of where it is can "twinkle" -- so it behaves erratically. Seven GPS satellites is "OK," but not good....if you see what I mean.

    Andy
     
  5. Derek Cooper

    Derek Cooper Active Member

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    Thanks for the link Andy - appreciate it.

    Is the Kp index a global index, or does it have regionality?
     
  6. Gary Haynes

    Gary Haynes Administrator
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    It is global. It is measuring activity from the Sun. Just remember that it is is an indication of events in the past not predicting the future. For that you need to look at a lot more solar activity data and my head bursts. I do that for doing long distance ham radio and still get confused. https://en.wikipedia.org/wiki/K-index
    The Kp index and estimated Kp index[edit]

    The official planetary Kp index is derived by calculating a weighted average of K indices from a network of geomagnetic observatories. Since these observatories do not report their data in real-time, various operations centers around the globe estimate the index based on data available from their local network of observatories. The Kp-index was introduced by Bartels in 1939.[1]
     
  7. Dave King

    Dave King Well-Known Member

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    Derek

    I don't 100% trust the log. I have found tons of bugs in the logging profiles and reported them. I trust the error you see more than the logged number of sats for real time. With that said I get the same issues you experience from time to time where it loses GPX fix and causes the copter to do something weird. After flying with it for so long I am just programmed to react to put it full manual mode and land. The great thing about MK is that you can have the voice comands and it will tell you promptly when it starts. When it starts just land immediately. Out of 3000 MK flights under my belt this happens about once every 75 to 100 flights on average for me.

    The Wookong on the other hand never has GPS hi-cups ever I can say that confidently after close to 800 flights on it this year but it can't do waypoints. Since the Wookong never hi-cups on GPS I have a hard time buying the issue of excessive metal in the area etc. I have flown both copters in the same exact spot where the MK has hi-cupped but the Wookong hasn't. I have also had the same issue with MK in multiple configurations including:
    1. GPS and Navigation board out on boom 1.
    2. GPS and Navigation board on top of flight controller.
    3. New GPS board with extended sat strength.
    4. External compass board.
    5. Internal compass only.
    6. Making sure all Lipo wires are short, taped up and always well below the compass.
     
  8. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I'm not sure that's quite correct, Gary -- but, as you know, I'm often wrong -- but rarely uncertain! :)

    The first link I gave predicts the KpIndex for four hours in the future. I seem to recall that photons from the sun arrive much earlier than the charged particles that disrupt GPS -- like one to five days. So the visual indications of a coronal mass ejection (CME) arrive after about an eight minute transit time, then NASA satellites need to observe the CME itself, assess its magnitude, velocity (and thus whether it's going to hit Earth), and thus its transit time.

    Here's the current KpIndex from that site -- you can see the vertical dashed line which is the current time and to the right, the prediction (and by the way, duck and cover, KpIndex is predicting a significant solar storm KpIndex = 6+)

    NOAA KpIndex Prediction.png



    Andy.
     
  9. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    The "p" in the K-Index means it's a planetary index as I understand it, Derek.

    Andy.
     
  10. Gary Haynes

    Gary Haynes Administrator
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    I was referring to the simple chart from n3kl.org It is in 3 hour blocks and seems to be the one found most often. So if you are early in the block at best you get a 3 hour prediction.

    Screen Shot 2015-09-07 at 1.45.43 PM.png

    Your example for the Air Force is more predictive with a bit more time range.

    That said the summary for today - STORMY. LABOR DAY GEOMAGNETIC STORM: The CME missed, but a geomagnetic storm broke out anyway. G2-class storms are in progress on Sept. 7th as Earth passes through a fast moving stream of solar wind. High-latitude sky watchers should be alert for auroras after nightfall.
     
  11. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Oh, sorry, Gary. You're are correct, then. Yeah, you only get a 3-hour prediction on n3kl.org.
    What I don't understand is why, given the transit time of the CME is 1-5 days, there is not more predictive capability. I suspect the magnetosphere interacts with the CME differently each time.

    Andy.
     
  12. Gary Haynes

    Gary Haynes Administrator
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    And it really STORMY out there.

    Screen Shot 2015-09-07 at 7.43.29 PM.png
     
  13. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Yup. Much worse than this and things are going to start going extinct around this part of the galactic quadrant! :)
    Looks like it's going to get to KpIndex = 8. http://www.swpc.noaa.gov/products/wing-kp
    Even my fillings will start to emit an aurora...

    Not a good time to fly with GPS Hold.

    Andy.
     
  14. Derek Cooper

    Derek Cooper Active Member

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    We HAD to fly early afternoon yesterday (EST) and certainly started to notice the impact of the rising K index. Toilet bowling witnessed... Such fun when you're flying an $80k payload! :eek:
     
    Jason Smoker likes this.
  15. Jason Smoker

    Jason Smoker Active Member

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    I wouldnt use the gps if the k index is that high, toliet bowling is never fun to witness or experience or when trys to fly off in a random direction. The joys of our trade :(
     
  16. Derek Cooper

    Derek Cooper Active Member

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    Yah, we promptly ended the day!
     

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