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Incorrect Altitude Readings

Discussion in 'Phantom 2 Discussion' started by neilnasdaq1, Dec 17, 2014.

  1. neilnasdaq1

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    Hey, I flew my phantom v 2.0 for the first time yesterday and noticed that it was changing in altitude during flight. Like it would ascend when I would not be touching the remote and it would descend. Its strange.

    EDIT

    Also, the altitude readings would be way off from the beginning. It would say -250 feet when on the ground. I have been researching, could it be a bad barometer? So replacing the naza v2 board would fix it? I just got it a week ago!
     
  2. N017RW

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    Re: Changing in altitude during flight.

    Have you done all the recommended out-of-the-box pre-flight calibrations.

    i.e. controller alone via USB to a PC or Mac, controller when connected to the quad via USB, full IMU, and then lastly the compass?
     
  3. SteveMann

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    Re: Changing in altitude during flight.

    How much? A few inches or ten feet? Also, in what wind conditions?
     
  4. Couchie

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    Re: Changing in altitude during flight.

    I fly the v3 and sometimes have the same issues of only a few inches when I'm closer to the ground (1-10' AGL).

    I'm still a newb to the phantom, but fly my craft much like I do an aircraft. In an aircraft when 'turning' or making some alteration to the current path of the craft there will be an exchange of energy. For example when in an airplane, flying straight and level and gently moving to a bank (turn) Some of the horizontal lift or energy is transferred to vertical lift or energy. If you don't correct for this, the energy moved to the vertical plain from the horizontal will cause the craft to descend unless some input is put in place to counteract that bit of energy transferred.

    Granted, the above example is due to the craft having a fixed wing but the spinning props will work relatively the same way. It can be explained much like a prop on an airplane. I won't bore you with an explanation of the P-Factor, but this is also another thing to consider when making some alteration to the speed, course, or altitude.

    So the short answer is, yes, the craft will change altitude in flight. More so with drastic changes to speed, course, or altitude.
     
  5. spudraleigh

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    Re: Changing in altitude during flight.

    A non-obvious answer is that you are flying into and out of restricted airspace. Again, all depends on how far you are talking about up and down, how far away you are flying, and where you are relative to a commercial or military airport. I live in the center of a triangle having as its vertices, a large commercial airport, a fairly large private airfield, and a huge military flight base. Sucks for me, I know :x Depending where I fly within this triangle, I can go different heights and have flown in and out of restricted space and seen the up/down phenomenon.
     
  6. neilnasdaq1

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    Re: Changing in altitude during flight.

    I live around 10 miles for a small airport, but when flying my V2+ I have no problem with this issue. I will try flying again tonight.
     
  7. Meta4

    Meta4 Moderator
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    Re: Changing in altitude during flight.

    If you don't give any information about this mysterious change of altitude people are guessing and no-one can help.
    How much is it moving? Give us some details.
     
  8. SteveMann

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    Re: Changing in altitude during flight.

    In a multirotor, there is no energy budget between straight & level or turning, all energy is directed to lift regardless of direction of flight. When you turn the A/C all you are doing is slowing the rotors on one side and increasing the speed on the other. (Well, the controller does it for you so you don't have to think about coordinating the differential). When you yaw, you are slowing the CC or CCW rotors and speeding up the others to maintain lift. Because the rotors are counter-rotating there is no P-factor since each CW prop is paired with a CCW prop and the P-factors cancel out.
     
  9. neilnasdaq1

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    Thanks for all your help! I think its a bad barometer. I tried everything, adv calibration, compass, nothing works...
     
  10. RobertMfromLI

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    • How much is it drifting?
    • Where are you getting your altitude readings? (for instance, the iOSD Mini is in meters, not feet, from launch elevation (not sea level)).
    • How many GPS locks do you have?
    • How many does it maintain when you experience this behavior?
    • What's your battery level? (a low battery will cause the copter to struggle to maintain altitude)
    • Are you waiting for enough GPS locks and home point recording before flying?
    • What position is S2 in on the remote?
    • What are the surroundings like? ("Canyon bounce" will affect altitude, as well as X/Y position maintenance, and can occur around big buildings, canyons, enough trees, or other objects, even with a LOT of GPS locks)

    The P2 will change altitude a bit when hovering - sometimes up to 3-6 feet (1-2 meters on the iOSD info), depending on a lot of factors. The discrepancy will be larger if you have few GPS locks.
     
  11. neilnasdaq1

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    How much is it drifting? - Lowering about 1 feet every 2 second. If I fly it for around 2 minutes or so, the phantom stops drifting.
    Where are you getting your altitude readings? (for instance, the iOSD Mini is in meters, not feet, from launch elevation (not sea level)). - I am getting the altitude readings from the dji lightbridge. its in feet.
    How many GPS locks do you have? - I get around 11 sats.
    How many does it maintain when you experience this behavior? - It maintains around 11 sats on the ground. Sometimes 13 sats when flying.
    What's your battery level? (a low battery will cause the copter to struggle to maintain altitude) - Battery always full when I test it.
    Are you waiting for enough GPS locks and home point recording before flying? I wait for sats, then calibrate compass, then wait for at least 9 sats prior to takeoff.
    What position is S2 in on the remote? - all switches are up.
    What are the surroundings like? ("Canyon bounce" will affect altitude, as well as X/Y position maintenance, and can occur around big buildings, canyons, enough trees, or other objects, even with a LOT of GPS locks) - I am in the middle of the park. Its a series of soccer fields.

    I was researching in to this issue and it may be a bad barometer. I might need to talk to DJI and get a replacement.
     
  12. RobertMfromLI

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    One last question:
    - What firmware are you running?

    The older firmware takes a few minutes of flying/hovering/playing around to maintain position properly. The newer firmware records readings it needs for magnetic declination issues and is more stable (and hovers or flies more accurately) from earlier on in each flight.

    Or inotherwords, the copter becomes more stable and more capable of maintaining position (X, Y or Z) after it's been flying a few minutes. That isn't a barometer issue. Keep in mind, IIRC, the P2 actually uses a bit of data (not just barometric altimeter) for maintaining position.

    My copter (on a very early firmware) used to drift in all three axis for the first few minutes of flight until I upgraded the firmware (which comes with a bunch of other considerations). Now, it's a lot quicker to become "stable" and maintain position on any axis.
     
  13. neilnasdaq1

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    I am on the latest firmware. 3.0.8
     
  14. neilnasdaq1

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    I am on the latest firmware. 3.0.8, but the problem is that the altitude isn't displayed correctly. It would say -250 feet when its on ground level.
     
  15. RobertMfromLI

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    :|

    Keep a record of plug positions (NOT by the way they are keyed, but by how they are wired) when you replace the NAZA-M unit.
     
  16. ianwood

    ianwood Taco Wrangler
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    Sounds like a bad barometer. If you're getting erroneous altitude readings and it is losing altitude consistently, that would be the prime suspect. To be sure, double check that your throttle has full range and is centered properly in the Phantom Assistant.
     
  17. N017RW

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    Bad barometer = bad Naza.

    They can't be separated.
     
  18. neilnasdaq1

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    I am going to return it back to dronesetc and get it repaired. I hope its quick!