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Professional Dynamic Homepoint Altitude

Discussion in 'Phantom 3 Help' started by TAZ, Jun 25, 2015.

  1. TAZ

    TAZ

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    Forgive me if this has already been answered...did a search and can't find the answer...

    So, in regards to the Dynamic Homepoint (setting the new Homepoint to the current birds location) I am wondering if it's current altitude should be where the bird returns to and hovers instead of landing or is landing fully at ground level, by design?

    I ask because, when you set the Dynamic Homepoint, the acceptance screen says "It will return to this point at minimum altitude of XX.X in accordance to your Failsafe settings" where XX.X is the birds current AGL altitude.

    ImageUploadedByPhantomPilots1435273027.372139.jpg

    The way I interpret that is the bird should climb to your failsafe altitude, return to the Homepoint, and then descend until it reaches the XX.X altitude which was set dynamically, and hover. Instead, it climbs to the failsafe altitude, returns to the Homepoint....and fully lands. Why is it not respecting the recorded altitude...and what is the meaning of that number if it isn't going to respect it?

    The reason for this question, is imagine you are launching from the deck of boat. You fly the bird a few feet above the deck, and set your dynamic home point. Then after flying, for some reason you lose communication with the RC... I'd expect the bird to return to its recorded position and altitude (respecting the failsafe altitude along the way)...and hover for easy retrieval once you've repositioned the boat from its drift. Instead, it's ignoring the XX.X and doing a full 0' land.

    Is this a bug, or by design, and if by design, what's the point of recording and reporting its current altitude?

    PS--This unexpected behavior can be duplicated in the Simulator.
     
  2. snerd

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    I'll take a stab at it......................... I don't think there is any such thing as a return and hover. Both the failsafe setting and RTH settings are implied return and "land". I may not be understanding your question, though, and my reply is just my opinion, not verified fact.
     
  3. bobmyers

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    The Phantom will land if not interrupted by the pilot. It will not hover.
     
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  4. TAZ

    TAZ

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    In the above example, it states "When required, it will return to this point at minimum altitude of 20.3 FT". Which, by my reading, explicitly indicates it will come back to its current position, and not go below 20.3 FT. However, it in fact returns to a minimum altitude of 0FT (landing). The 20.3 FT indication is both misleading and unused as far as I can tell. Maybe I am the only one that finds the above message misleading.

    It would in fact be a very useful feature if you could set a return point that happens to be above ground (over water or rough terrain making an actual landing undesirable). And the above message implies that is what it will do, but the behavior is landing (why even say its current altitude, if it's not recording it as part of its "position"). Programmatically they had to write code to record, and communicate the current altitude to present the "Aircraft Position as the Home Point" message above, but it doesn't seem to be adjusting its behavior by that number...

    I was just curious if the current implementation is as conceived, with a misleading on screen description....or if it isn't currently implemented as originally intended.
     
  5. bobmyers

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    I don't think we know that answer and DJI will probably not offer a clarification. Just don't expect it to hold altitude and not land if RTH is activated and pilot input does not interrupt the RTH command. On another point, it is going to land anywhere that power reaches a critical level-- and it will probably be in the RTH mode at that time--automatically.
     
  6. SteveMann

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    I don't have a P3, but the P2 is probably similar. The operative word is "return" at a minimum altitude of 20.3 ft.

    In the P1 and P2 the Phantom will return at the RTH altitude or the current altitude, whichever is higher. When it commences to land, the altitude is completely irrelevant - the Phantom will descend until it won't descend any more, then after a few seconds the motors shut off.
     
  7. Akrosfer

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    Here is my own answer:
    The UAV will always keep the altitude of the first homepoint recorded. Once you order it to land on the dynamic homepoint automatically, the UAV will arrange its altitude ( first homepoint + XX,X ((if it already has a bigger altitude, it will not descend) and fly exactly to the dynamic homepoint. Later on, it will just land. It looks like an incomplete but affective (in particular situations) ability of the Phantom. You are the one who should think about the dynamic homepoint altitude.
     
  8. TAZ

    TAZ

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    Thanks for the comments. I do understand the birds behavior in RTH situations, what I was pointing out is the screen we are presented, doesn't accurately describe its behavior... Given this screen is relatively new (just added last rev) it's the only "documentation" we have...and it is inaccurate.

    Just to be clear, in spite of the screen saying "When required, it will return to this point at minimum altitude of 20.3 FT", that is actually untrue. Instead it returns to this point at a minimum altitude of your fail safe altitude (or higher if your bird is higher when RTH initiated). The 20.3FT number is not a factor at all when describing its behavior.

    Maybe the problem is best described thus way. If you fly to altitude X, and press the button to set your home point to the current location, rather then the screen reporting the bird will fly back to the current position at a minimum of altitude X, it should in fact state it will fly back at a minimum of your failsafe altitude.
     
  9. TAZ

    TAZ

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    I get what you're saying, but that's not entirely accurate. The XX.X I used above is a number presented on screen of your aircrafts current altitude above takeoff, when you press the button to reset the Homepoint. The bird does not fly back using first Homepoint + XX.X as a minimum...it uses your failsafe altitude. The XX.X is superfluous, and unused.
     
  10. Akrosfer

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    Example:
    a. The altitude of your first homepoint ground: 800 m.
    b. The failsafe altitude arranged: 40 m. -> 800 + 40 = 840
    c. The altitude of your dynamic homepoint ground: 780 m. (not the altitude of the UAV)
    d. The present (last) altitude of the UAV: 810 m.
    If you order the UAV to fly back to the homepoint automatically,
    1. It will ascend to 840 m (*)
    2. It will go to the coordinates of your dynamic homepoint.
    3. It will descend (as much as the failsafe altitude) to 800 m. (**)
    4. It will probably descend slowly trying to find the ground ;)

    * A second possibility, it can be 850 m (810 + 40)
    ** A second possibility, it can be 810 m.

    I guess second possibilities won't be much helpful.

    Either way, the dynamic homepoint system needs your attention especially about altitude differences (homepoint 1 vs homepoint 2) and/or (homepoint 1 vs dynamic altitude of the UAV).
    You should also keep an eye on the obstacles on the route.

    Better use it on sea on a boat. It will probably work perfect, as the ground level is always 0.
     
  11. N017RW

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    Kinda confusing to use altitude above mean sea level (800m) as the system associates the home point's ground level to be Zero regardless of true altitude above or below sea level.
     
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  12. TAZ

    TAZ

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    Wow, that's about as clear as mud. No offense intended, I just believe you're missing my point and confusing the issue. Understandable, as I also was confused between what I knew to be true with RTH altitudes, and what I was seeing on the screen. The problem is the discrepancy to what you are describing as guessing to be true, without actually testing it and seeing it's true behavior and noting the misleading on screen messages I am describing. If you do this hopefully enlightening example, you may see my point.

    1) Set your Failsafe altitude to 20M (65.6FT)
    2) Fly out at a distance with a height higher then 20M (let's say say 40M ~131FT) and set the Homepoint to your current position. The on screen message will indicate "...when required, it will return to this point at minimum altitude of 131FT" your current aircrafts altitude.
    3) Fly your bird to another location and descend to an altitude of 10M (32FT)
    4) Hit your home button.

    If one is to believe the on screen display "it will return at minimum altitude of 131FT"...one might expect it to climb to 131FT. However that is not the case. It will actually only climb to your Failsafe altitude (20M or 65.5FT). The return to home altitude is in no way influenced or reflective of the altitude indicated on the screen when you reset the Homepoint to your aircrafts current position.

    To hopefully put a stake in this issue and kill it, when you press the button to set your Homepoint as your current aircraft position, the screen reports the aircrafts current altitude as what will be used as the minimum. The on screen message is wrong and instead your Failsafe altitude should be factored into a full understanding of RTH altitudes as indicated in the manual. Test it out and you can verify this to be true.
     
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  13. Meta4

    Meta4 Moderator
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    To clear up some confusion from your original post ...
    What you are describing is not dynamic home point.
    Setting the new Homepoint to the current location of your Phantom is resetting your homepoint.
    http://abovephotos.smugmug.com/photos/i-GpMJWTf/0/M/i-GpMJWTf-M.png

    Dynamic homepoint is where you set home point to be wherever your phone/tablet is as you are moving. Your Phantom monitors this and updates its homepoint every few seconds. In the event of a RTH, the Phantom returns to the location of your mobile device at the time the RTH was activated.

    In all cases the Phantom will RTH 20 metres (or whatever RTH height you set) above the home point, unless it is already higher than that, in which case it will stay at that higher level for the RTH.

    If you are flying from a moving boat, dynamic home point may be more useful than simply resetting the Phantom's current location as home.
    But you should be ready to cancel RTH as the Phantom gets closer and resume control as the Phantom will descend until it lands and this is not a good thing over water.
     
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  14. Akrosfer

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    You are a good moderator indeed. I will be following you ;)
     
  15. davefales1

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    If I launch P3S by hand, will the Home Point then be set to the altitude of my hand?
    In which case, on RTH, it will descend to hand altitude and then what? Will it shut off the rotors?
     
  16. bobmyers

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    no it wont shut off the motors-- the homepoint altitude will be off by six feet or so and the telemetry will show - 6ft +/- at the home point.