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Stupid question.. Compass

Discussion in 'Pro/Adv Discussion' started by Prostock85, Jun 13, 2015.

  1. Prostock85

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    For the record, I'm new to this site (awesome) yet have flown before but have what I perceive a question I haven't seen asked in the hours of reading I've done so far.

    Why does the compass have so much bearing on what happens? I mean, if I'm in the woods and someone gives me coordinates lat/long I can figure out where I'm going, including direction. I'm baffled why even in a totally failed calibration or even flying near metal can create such havoc when it could essentially fly with gps alone. I've been doing my a ton of reading because I want to take off and land on an aluminum pontoon boat and was trying to see what affects what and why. Any Ideas?
     
  2. UKFlyer

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    Yes but what if you did not know which way was north or south? The phantom also needs to know this. The compass works in conjunction with the gps. As for landing on a aluminium boat i'd hand catch it just to be safe.
     
    snowghost likes this.
  3. Prostock85

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    Yes, but if you loose compass it would just spin. Using gps alone, once you move forward/backward/left or right, your heading could be calculated. My gps on my boat doesn't have an actual compass, it's calculated as we move.

    Also, as for the catching it upon landing... Should I turn off vps and just use gps so the water doesn't freak it out?
     
  4. UKFlyer

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    To be honest i'm not 100% sure either why it does actually need the compass because as you say once in movement it should in theory be able to work it out, i'm sure someone else will come along with the answer. As for VPS i'd definitely turn it off over water as it could confuse it, mines turned off all the time anyway.
     
  5. marg2

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    N------->S <W______=__________>E just so he knows where is at! Aluminum wont have any interference on it
     
  6. Meta4

    Meta4 Moderator
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    Your aluminium boat shouldn't be a problem and neither would a copper, silver or gold boat .... but if it was iron or steel that's a different matter.
    On boats, hand catching is the way to go rather than letting RTH land for you.
     
  7. ianwood

    ianwood Taco Wrangler
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    The compass does what an analog compass does for us. It tells us which way we are heading. As stated above GPS has no concept of heading. It can only determine "course over ground" by comparing two or more GPS points that are at least several meters apart. Even then, it would be inaccurate as result of GPS drift, wind and other factors.

    Even more important than the heading, the compass plays a critical role in overall stability. It provides an absolute (as opposed to relative) reference to the direction of gravity.
     
  8. Prostock85

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    Didn't think non ferrous metals would affect it but just wanted some confirmation. Thanks

    Completely understand, just figured one may reference the other in terms of a failsafe. Possibly have the option to turn off compass in an emergency such as erratic behavior. I think I would rather try and land a wandering craft vs one that's uncontrollable. Once again, I am by no means complaining since whomever built these are waaay smarter then I am. Thank you all for your replies.
     
  9. ianwood

    ianwood Taco Wrangler
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    The problem with the compass is it is very hard to know when it is reading accurately vs. being interfered with. DJI has tried to tighten their error detection on the compass but I personally believe it is now too tight. I think there are times when the P3 is reporting compass issues when there are none.