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How does ground station deal with varying ground levels?

Discussion in 'DJI Ground Station' started by 049derek, Dec 17, 2014.

  1. 049derek

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    Hi guys

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

    How does ground station deal with terrain that isn't level?

    For example, if 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.

    Does the aircraft continually measure the actual altitude, or does it just use the level of the starting point?

    Any ideas?

    thanks

    Derek
     
  2. 4wd

    4wd

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    The phantom and app have no understanding of the local topography - you have to set suitable altitude manually.
    It's a good question whether you can set a minus altitude - if you fly below your start point normally it will show a negative figure so would be interesting to try.
     
  3. SteveMann

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    The Phantom uses a barometric pressure sensor in the main controller to determine altitude which is set to zero when the home point is established.
     
  4. 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.

    I don't think ground station accepts a negative altitude for a waypoint, I must still try that. If not it means you can't get down to the river below unless you maybe set a new home point on the bank of the river I guess?
     
  5. Realist

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    Just purchased a ground station so if I take off that's in affect zero home point and if I choose a location that's as for example:

    Location 226 meters showing on map I presume is above ground level.

    So is that reading also ground level at the other end point 2?

    Point 1 home zero
    Point 2 on map showing as 226 Meters Above Ground Level.

    So when it reaches point 2 is it at zero ground level or 226 meters above ground level and whet if there was a higher mountain in between say 230 meters how does it handle that?
     
  6. Realist

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  7. TeamYankee

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    If you fly from home point (zero meters) and climb to 226 meters then all will be well. If there is a larger object in the way then it will simply fly into it and crash!

    Just think of the map as a flat land area... and adjust your way points according to what you determine is a safe altitude to miss the objects on the way to the way points.

    It does not follow the terrain automatically, you have to do that yourself with way points.
    Check this out for some ideas of what can go wrong if you have guessed the wrong height:

     
  8. SteveMann

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    Wow, that was one very lucky Phantom owner. Look at 3:18 in the video.
    I know you aren't looking at FPV, but if the object is below the horizon, it's below you.
     
  9. Realist

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    WoW one lucky chap inches from loosing his quad.
     
  10. Questor

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    I think Ground Station was designed to sell more Quads.... :D

    Very lucky flight.
    Q~
     
  11. 464chief

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    So much for spending $$$ thinking the optical sensing system would let you navigate Above Ground Level altitude, I crashed trying to set waypoints at 2 meters. The P3 ended up bouncing on the ground.
     
  12. PTCX

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    Altitude is the least accurate sense our Phantoms and other similar machines have.
    After using GPS for a long time I have learned not to trust altitude readings much and always treat it as having an error margin of at least +/-20 meters.
    I'm not sure of how accurate or what level of error is in the barrometric sensor but I would not trust it to be absolutely accurate either.
    When I start flying GS missions I will not be setting any waypoints lower thn probably 50 or 60 meters until the system shows me it can be trusted to be somewhere near safe to do so.

    I did have a plan to put a flytrex into either my Phantom or the S550 and first do a manually controled flight over the area I plan to fly a GS mission over and check the hight of trees,hills or stuctures in relation to launch/home point and set waypoint altitudes based on those readings plus a safe margin but it is proving difficult to obtain a flytrex unit.
    Looking for alteranive telemetry units.