Welcome to PhantomPilots.com

Sign up for a weekly email of the latest drone news & information

Phantom FC40 - not locked in

Discussion in 'Phantom FC40 Help' started by Curb, Feb 3, 2014.

  1. Curb

    Joined:
    Feb 2, 2014
    Messages:
    22
    Likes Received:
    0
    I'm experiencing something like slow drift on all axis's. It feels very loose and definitely not locked in - with more than 6 satellites.

    There was a little wind today - around 5-7 mph and it was moving around in I'd say a 2m x 2m 'box' when hands off and around 4 metre's up. Is this normal? When I took it up I'd say 50m or so and it was pushed by the wind which was most likely much faster. It drifted 6-7 metre's or so and needed input to stop it drifting away all in GPS mode. Maybe I'm expecting too much from it. I thought the Naza M v2 would have held it better. Is there anything I can check to make sure it's not my error?
     
  2. Big Ben

    Joined:
    Jan 17, 2014
    Messages:
    344
    Likes Received:
    0
    Apart from the limits in accuracy in determining the geographic position through the GPS signals there is also the update rate of the receiver to consider. For most consumer grade receivers the position is updated once per second. For marine or consumer grade car navigation this is usually sufficiently accurate. For high speed navigation a higher update rate is desirable. Professional grade receivers can go up to a 20Hz update rate afaik. It's highly unlikely the Phantom has such a receiver. It *may* have an update rate higher than 1Hz. Maybe 2 or 5Hz. I very much doubt it will go higher, if at all. In between position updates it possibly/probably uses an accelerometer and some 'dead reckoning' to calculate the position between the GPS updates. Stronger and more turbulent wind will cause greater deviations from its position. If at the same time the GPS satellite coverage is low and the position is less accurate the Phantom will hold its position with equally decreasing accuracy.

    Since I have not yet received my FC40 (Update! Update! It is scheduled to arrive tomorrow afternoon according to the Track & Trace information I just checked :D ) I have not yet been able to observe any possibly visible frequency with which the Phantom may update its position. I will look for that.

    You could experiment with increasing the basic gain for faster position corrections.

    (Unfortunately the Prop Guards I also ordered were out of stock and I will receive those later. Hopefully this week. Will have to wait for them to make my first flight. If I don't and damage ensues I WILL be very angry with myself which WILL spoil the fun. Don't want that. :roll: )
     
  3. Curb

    Joined:
    Feb 2, 2014
    Messages:
    22
    Likes Received:
    0
    Cheers for the detailed reply. I didn't do an IMU calibration, so maybe I need to re-calibrate everything I can.

    Prop guards shmop guards I thought - then managed to to a front tip over on my first take off attempt straight into mud!