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??? My Altitude Readings start at -350 on ground ???

Discussion in 'Phantom 2 Vision + Discussion' started by flyingtim, Jan 2, 2015.

  1. flyingtim

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    Any ideas? Yesterday my altitude readings started at -350 when sitting on the ground. The higher I went the numbers worked their way to Zero eventually.
    Any ideas on what causes this?

    Thanks
     
  2. LordEvil

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    Try the compass dance again see if that helps
     
  3. Fplvert

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    :?
    That is way off. You should do an advanced IMU calibration while the bird is cold.
    Generally, the altitude values go up as they warm up. You should always cycle the bird after your field calibration and make sure your home lock readings are close to actual to prevent a possible flyaway (loss of satelights going to a different home).
     
  4. Meta4

    Meta4 Moderator
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    Really ?????
    The compass has nothing to do with altitude readings.
    Compass calibration is not the universal fit it all.
    Fplvert has given the proper fix
     
  5. LordEvil

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    Lot of "?" might try a compass dance to help correct to just 1.
     
  6. Meta4

    Meta4 Moderator
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    The OP only mentioned a problem with altitude readings.
    Compass is all about north, south etc.
    The compass only understands 2 dimensions - nothing at all about altitude.
    It is 100% unrelated to the OP's question.
     
  7. aartsf

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    +1
     
  8. CapnBob

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    The compass has nothing to do with altitude; it is for heading only.
    The bird gets altitude readings from GPS and the NAZA altimeter.
    The thing to remember is that GPS, while great for position, is seriously weak in the altitude category.
    An altimeter is more accurate, but you must know the barometric pressure at the particular time and location,
    and it must be compensated for in the altitude calc, which cannot be done in the existing hardware.

    Aircraft pilots are constantly advised of the local "altimeter" settings by A.T.C. for that very reason. ("two niner, niner two", etc.)

    If you have a large storm approaching, and the B.P. drops, you will get a different altitude reading sitting in the same spot.

    The bird uses the altimeter in a relative way to hover; it just tries to keep the reading steady.
    It is not accurate for an absolute altitude reading.
     
  9. Meta4

    Meta4 Moderator
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    Because the Phantom doesn't attempt to give an altitude above sea level but only gives altitude relative to home point, and because a typical flight is 20 mins or less, correcting the barometer isn't necessary. It's accurate enough for our purposes.