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Planning Altitude

Discussion in 'DJI Ground Station' started by job2310, Oct 25, 2014.

  1. job2310

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    This has probably been asked 1000 times before but I can't find a documented answer (that I can understand). When using ground station is flight altitude AGL or relative to the home point altitude?

    For example, if I take off from the top of a hill and climb 30 meters and then proceed to fly over a valley does the bird drop down to 30 meters above ground level or would it fly at the original height until I changed the altitude with a waypoint?

    I think the answer is it would stay at 30 meters above my home point but I want to confirm.

    Thanks.
     
  2. Timsytanker

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    Yep, it's all relative to your home point elevation.
     
  3. paulajayne

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    Altitude is based on ambient pressure at time of take off so altitude would be based on home point. Do not think the GPS altitude is taken into account - I stand to be corrected.
     
  4. job2310

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    Good stuff, thanks for the feedback.
     
  5. 049derek

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    Hi guys

    I am using the Phantom 2 Vision Plus - ground station built into the app.

    So if the ground station altitudes are all relative to the home point, how do you solve this one?

    Your starting point is high up on a hill and you want to set some waypoints fairly low over the river below. The heights of those waypoints will be negative relative to the starting point.

    Any ideas?
     
  6. josephbelt01

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    Sounds like a good way to crash into terrain. You can try a negative number but I'd be careful.
     
  7. SteveMann

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    GPS altitude is unreliable. Even the best manned aircraft GPS units will have a 7 to 10 meter vertical error which is why GPS approaches are higher than ILS approaches which have a vertical error tolerance of +/- 1.4 degrees. At the IAF if the ILS needles are centered, I am within 70 ft of my target altitude 20 miles from the airport. And the glideslope error decreases as I get closer to the runway.
     
  8. Bibos

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    Just a Little correction. The Altitude shown in the APP is not based on ambient pressure at time of take off but on ambient pressure at time of power-up of the Phantom. This can be a big difference :D
     
  9. 049derek

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    I checked on the weekend. Powered up and took off in a valley and flew to the top of a hill. The altitude showed 120m even though the ground was about 10m below the aircraft. So yes, zero is where you power up, and everything else uses that zero as a reference.