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Height telementry is off

Discussion in 'Phantom 2 Vision + Discussion' started by Sasquatch, Jul 10, 2014.

  1. Sasquatch

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    I asked this question awhile back but it must have gotten lost in the shuffle.

    Anyway, the height being reported from the app is always telling me that my bird is 10-15 feet higher than it actually is. I've done 3 compass calibrations and in the software it tells me I don't need to calibrate my compass. Is this even a compass issue?

    Any thoughts or help would be much appreciated.
     
  2. Mako79

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  3. Sasquatch

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    Thanks, but that person's problem isn't solved. He still says he's got a height telemetry issue after advanced calibration and reinstalling the software.
     
  4. Sasquatch

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    Can't anyone help me with this concern....should I be concerned?

    My bird flies well and smooth and now on my 7th flight I haven't noticed any other issues. The only thing I noticed was on my 6th flight while trying to land. As I was descending and got about 1 foot above ground, the bird was bouncing quite a bit before I touched down. It was actually bobbing up and down pretty radically but this was the first time it ever did that.

    I truly hope someone can shed some light on the height telemetry thing.
     
  5. Mori55

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    I had a Asus HD memo pad , brand new.. The distance was 800' off. Took it back and got a iPad mini wifi only and all was fine , also worked great on my iPhones . Just didn't work right on that device. Do you have a iPhone you can try it on ? The distance is recorded fom where it gets it's home position.
     
  6. Sasquatch

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    Thanks for replying Mori55,

    I actually use an iphone 5 for my FPV device, I have no others at the moment. As I said, I'm not even sure the height telemetry being off 15-20' is a problem or issue. I don't even know if this is 'normal' or within acceptable parameters. Maybe it's not a problem? As for distance, that is harder to tell, but from what I can tell, it's fairly accurate.
     
  7. 8676309

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    How are you determining what the height "should" be? Maybe you're actually 15' above sea level and it's a units problem? Would help if they said in the application if the altitude was Above Home Point, AGL, or AMSL.
     
  8. lsteigerwalt

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    The bird bounces at 1-2 foot cuz of the bubble of air it's riding on at that height. All copters have this problem. It's always better to take off hard and fast and hand catch. Less chance of crashing this way.
     
  9. Sasquatch

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    Maybe I am that amount higher than sea level...I really don't know. I had pondered this idea but I don't think it's the reason and unless there is something that is mostly unknown about height statistics. This is what I'm trying to find out because I have no clue or idea why the app is saying my bird is 15-20' higher than it is. :?
     
  10. N017RW

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    The a/c uses pressure altitude.

    It does not care about elevation referenced to sea level.

    It's a relative measurement compared to the atmospheric pressure prior to take-off.

    Measurement accuracy/repeatability is effected by several environmental factors as well as economic ones (i.e. sensor quality, i.e. it's cheap).
     
  11. Sasquatch

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    Thank you very much for responding. The strange thing is, only on my 6th flight and after always landing on the ground, this was the first time I had seen this behaviour. I do know about the hand catching technique, but not sure I'm ready for that yet. I thought maybe it was something in the pavement on that particular spot I was trying to land on....magnetic rocks or something in the asphalt.
     
  12. slothead

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    The height readout that appears on the phone/tablet is not altitude above sea level. It is altitude above home. Your altitude above sea level is irrelevant. I also don't really know whether the readout you see on your phone/tablet is a metric the system uses or not, but I think it is only a data point made available for the operator only (real telemetry). If it is only operator information, then it won't affect your landings at all (unless psychological and affecting how you control your landings).
     
  13. 8676309

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    How do you know how "high" it is?
     
  14. 8676309

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    I don't think that can be. Isn't the home point set when you take off? Because if so, then when you first start up the Phantom at a new location and connect (before taking off) the home point would be either undefined or the home point from the previous flight. Both of these references would be invalid.
     
  15. Sasquatch

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    Ok thank you.

    In this topic, I was referred to another person/topic having this same problem but, the difference is, that person's bird height telemetry was off way more than mine...by hundreds of feet. Is this just something I have to deal with or do I need to look into replacement parts? Will it endanger my bird in flight and should I ground her for the mean time? As I've mentioned, I don't seem to have any issues with flying her otherwise, but I don't want to take any unnecessary risks either.
     
  16. Sasquatch

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    Thanks Slothead...this is what I figured as well.


    I have my settings set to 'feet' for height and distance. This does seem to be the case as well and so far, the misleading height telemetry numbers haven't been an issue for flying my bird and/or landing her. I'm just being cautious and trying to figure out the reasons and IF there is a chance it could be a problem.
     
  17. N017RW

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    It will not cause a flyaway or other issue except possibly RTH altitude issues. Haven't thought about it much really.

    The pressure sensor is part of the IMU which is inside the Naza-M V2.

    That's currently $200+ USD.
     
  18. cahutch

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    The compass has nothing to do with measuring altitude.
    Neither is the GPS used for altitude. It uses a barometric pressure sensor which will not be 100% accurate and will not match GPS or whatever other method you are using to determine what the actual altitude is.

    Also, I have read that temperature affects the barometric altitude sensor and that when you turn it on and it warms up the altitude reading will change even with it sitting on the ground. That may be what's throwing off your readout.
    Try turning it on and letting it warm up and watching the altitude readout as it warms up. You may be able to re-set home after it warms up before takeoff.
     
  19. N017RW

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    Who mentioned compass?
    I missed it.
     
  20. 8676309

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    Where does the barometric pressure sensor get its zero-reference? Anyone? Home point, but is that even defined before taking off?