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What Happened Here (HealthyDrones Included)

Discussion in 'Pro/Adv Discussion' started by Basald, Sep 12, 2015.

  1. Basald

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    This has happened to me more than once, this time, I landed upside down in the sand...needless to say I did not send in the bird to DJI, now have bullet connectors on my motor wires, and am back in the air...but still, wtf? We are hypothesizing the concrete has rebar within it, as it is a "vessel launch ramp"

    Open for comments[​IMG]
     
  2. isopro

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    Always check compass sensor value before every take-off, even in the event of a touch and go, or battery change. If you sense any GPS unstablility swap to ATTI mode FAST !
     
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  3. Basald

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    All values were good where I took off from (hence the edge of the concrete circle due to rebar theory) - 16 or so satellites connected, auto take off was used, and literally as soon as it popped in to the air, it put itself in atti mode without me having to flip anything and that line is my attempt to fight 15kt side on shore wind without damaging all the gear that was around (satellite imaging is 3 years out of date, these days there are about 100 kite surfers at this spot. I actually bounced it off the deck (gently) a few times but the props wouldn't shut off fast enough. Max altitude was no more than 30 feet, but i notice it thinks I was subterranean...is that a factor?
     
  4. III% Streve

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    How are you getting from a GPS issue to metal in the concrete?
     
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  5. Basald

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    It is just a theory, but if there is a checkerboard of rebar within the concrete, I would expect the GPS to have a very hard time seeing any movement over the area...think about your eyes like a satellite and you're drawing a line on a black piece of paper with a black pen...

    I cannot set my home point anywhere except the perimeter of this concrete circle and even then it often does not record correctly.

    The other theory is I still don't know what "Stop controller from sending NAN command which can cause aircraft to crash" means from the patch notes.

    More interesting info. I flew over this area and hovered at 30 feet, at the edge of my naked-eye vision, sure enough after about 15 seconds, about 3000 ft out, my monitor went black and RTH initiated. It actually reached 350 feet and moved away from the concrete circle before I got the monitor back.

    But I'm still not convinced
     
  6. III% Streve

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    GPS doesn't "see" anything. Its nothing but a series of frequencies constantly pinging. The P3 "sees" however many of those frequencies and determines its location by measuring those pings and their overlap. The compass would DEFINATELY not like all the metal as its all magnetized.
     
  7. Basald

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    Before I berate you, perhaps I am missing something...Would you please elaborate on what you think the cause for the Phantom losing 15+ satellites within 30 seconds of take off and never maintaining position hold for even one half of one second is? Your post does not make it clear, and I am trying to better myself so I'm asking for clarification rather than thumping on you with my keyboard.

    edit^Sorry but I have to defend myself against your explanation of GPS technology...the analogy I made was in layman's terms for a reason. Your explanation of how the GPS works is exactly why I used layman's terms. I am well aware a GPS does not use the sense of sight. Thanks for clarifying though.
     
  8. reboot81

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    Location:
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    How's GPS reception/accuracy with other GPS devices in the area? Your iPhone can detect strong magnetic field with this app.

    Anyway, if a location seems unfavorable only once, don't trust it again. Use another site.
    Did you calibrate the compass at this location?
     
  9. III% Streve

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    My most recent post was not meant to address you crash situation. Only to help you to possibly better understand how GPS works. That because what you said couldn't be more wrong. Its just as important that others that don't know don't learn something completely wrong as it is for you to know what's right. Reading your description of GPS function was severely flawed. That description was a response to my asking how you were morphing a GPS issue to a compass issue, and how they were related. In reality, there is NO tie between GPS and compass function, in a DJI product, or any other GPS enabled product. The two are co-reliant systems. But can function completely fine alone.

    What we do know is that you flew from a known source of magnetic interference. And we know that at some point a severe spin was induced. WE don't have video, logs, any idea what you calibration practices are, or answers to several question asked of you. That's likely why you have had little to no response to your thread. Ive been TRYING to help you understand what happened.. but with this last little rant... I'm done. Good luck!
     
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  10. Prometric

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    I watched a video on here about a guys experience with how sensitive the compass is. The user attached a tracker device on is p3a, and used a small tether with a small metal ring like on a key chain. This was attached to the arm located close to the compass. The tether free floated on the landing gear, so it was able to slide around a bit. When the user took of for the first time with this new device the p3a went haywire, but was able to land the craft. He realized what he had done and removed the metal ring and all was normal again. Most rebar in a slab of concrete is probably only an inch or so down. I try not to take off from any concrete surface.
     
  11. BudWalker

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    Did you do a compass calibration while on the concrete pad? And, what FW were you using?
     
  12. Basald

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    Other devices have little to no GPS reception from this pad.

    Steve, I'm confident that you are "one of those personalities" who is an expert on everything you have limited working knowledge of. I do not believe you would not be able to help figure this out, so thank you for being done. I never asked for clarification as to how GPS works. I assume you are one of those pilots who says they fly around metal objects all the time and do not lose GPS reception, therefore metal objects do not interfere with GPS...that logic is severely flawed...

    I'm curious how you *know* that a *severe spin* was induced, from my words as well as the posted screenshot from healthy drones. Again, more self-proclaimed expert speak. I can tell you matter of factly the copter did not spin at all. Less than 180 degrees the entire "flight" if you can call it a flight. The reason the line goes sideways and away from the shore, is due to wind direction and wind speed. I already stated that

    I calibrated the compass about 100 feet away from this location...but the compass didn't seem to be causing any problems, the GPS was misbehaving. I was using FW 1.3.2 and the update came out while I was waiting on replacement motors to arrive. It flies fine now, although one of the new motors has a bit of a metallic ping on the start up pulse. I'm swapping that corner out to yet another spare motor. It appears the 2312 motor cannot be disassembled for cleaning.



    It is probably the location. It might not be however. If anyone really wants to see the dat file, I have it, I posted the most relevant piece of data from the "log" The full CSV says the same things and KML shows the same
     
  13. BudWalker

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    Actually, I'd be interested in the DJIFlightRecordXXX.txt file if you could post that.
     
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  14. reboot81

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    Why are you then flying from this pad? Or did you mean "interference from this pad"?
     
  15. BudWalker

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    @Basald, could you please post the DJIFlightRecordXXX.dat file.
     
  16. Basald

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    yes, I am not home until Monday. Will be done


    I do not remain on the pad when flying but I do take off from the edge of it; because it is the only level surface in the area and I am not comfortable hand launching. I guess I'll have to get comfy with that process. because even takeoffs only and catch landings have all but destroyed the landing gear feet and legs both. It's not the smoothest concrete to say the least.