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AGL and true ground height

Discussion in 'General Discussion' started by kenjancef, Oct 26, 2015.

  1. kenjancef

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    That's great info about AGL and true ground height. I never realized that. I have an area near me that has some pretty big hills, say 50-60 feet high or so. So if I decide to climb up, I already loose 50 feet to the hill, if I understand correctly, right? What happens if you live in Denver??? (seriously...)
     
  2. Chuck Young

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    It is all the same for AGL calculations for the Phantom. I am in Colorado 3000 feet above Denver at 8000 ASL. Many of the places I fly are pushing 12,000 ASL, no problems except when you take off and fly over a canyon. At that point keeping your head on a swivel, ears wide open and a thorough pre-flight with a good TOPO is very important.
     
  3. kenjancef

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    Holy crap! That's pretty high to start off at! Yea, no falling asleep at the wheel there... yikes... And I'm afraid to fly over water! lol...
     
  4. Chuck Young

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    Here was today's flight. I was getting some footage of a slope rafters and kayaker's use to access the river downstream of the lake I live on. I think we are going to be able to get some funding for some improvements for river access. It is pretty steep and rough and needs improvement. I am kind of tentative about flying over our Lake. On this one I hit the 400 foot limit but probably could have flown 100 feet in two directions and could have continued up. 7700 feet where I took off and 9200 feet ASL 3800 feet North of where I took off from.


     
  5. kenjancef

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    Awesome scenery!

    Not to keep this off-track, but just one more question: So you start at what the Phantom thinks is ground-level, then you fly over to the cliff and canyon... what does the Phantom do in that regard? Would it think it was in negative height? Do you fly manual? Am I making sense?
     
  6. Chuck Young

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    I have to police myself and always keep an eye on altitude. Altitude displayed on the screen is from the takeoff point. I almost always have my max altitude set on 500 meters. I never know what is going to happen and where and when it will happen. Having the max for 500 meters allows me about 1600 feet vertical capability but to stay within the 400 feet AGL I have to be flying up hill. It is almost never a problem here to fly up hill. It is where the FPV goggles are very helpful for watching the treetops, sometimes you think your are trimming the tops with the props. Hehe

    I always adhere to the 400 AGL an encounter with that rare airplane or medivac helicopter would be a game-changer.
     
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  7. GadgetGuy

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    Open water is the safest surface to fly over. Clear LOS for miles, no potential for running into anything above ground, and no WiFI interference. It's just not very interesting. However, don't be afraid to fly over it to get to your destination. If your craft "falls out of the sky", it's done anyway, whether over land or water, and the fish won't sue! :p

    Only mine fields are Autolanding, so make sure you never get into an Autoland condition over water. Keep battery level above 10% and don't initiate RTH within 65 feet of your launch point over water! :eek:
     
  8. kenjancef

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    Yea, I had a strong eye on my battery level, and you're right, if it crashes, it crashes... There was a potential for some interference being that some heavy-duty power lines were about 1/4 mile away, but I had no issues. I was aware that there could be a problem, so I was very alert.
     
  9. Chuck Young

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    I need to get in a habit of putting floats on my quad just in-case of a water ditching. I am pretty sure I can fix it if it lands in the super clean water of our Rocky Mountain High super clean lake water.

     
  10. GadgetGuy

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    Where you launch from is always ground level zero. That is 0 for all Phantom altitude calculations. If you fly below that elevation to an area below you, it starts reading in negative numbers. Everything works just as if positive numbers were displayed. If you lose your aircraft signal, it's far safer to climb above 400 feet above the ground below your aircraft, until you regain control, than to lose control, while limiting yourself to a 400 feet maximum setting in the app above your launch point. Stay below 400 feet if you can, but safety first! Regain control, and then descend back below. I set mine at the max of 500 meters, even though I rarely ever need to exceed 400 feet. It's a safety cushion to not put a 400 foot lid on regaining control. DJI even says to increase altitude to regain control in their video. On the otherhand, if you have a circling helicopter directly above your bird, and lose control, better hope that RTH doesn't kick in and make it ascend to your 400 foot RTH elevation!
     
  11. GadgetGuy

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    Get out your scuba gear!:D
    Never leave home without a fully charged battery, and never fly downwind, hoping to get back in the same time it took you to fly there, and switch to ATTI mode for fastest speed and least battery consumption to get home safely!
     
  12. Chuck Young

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    Scuba has it's own set of problems when the lake is 8000 ASL.

    Almost had to go to ATTI the other day. Flew about a block down wind, it took forever to get back a block. The hand catch was fly up wind and grab it as it goes by with the next gust of wind. :eek:
     
  13. Chuck Young

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    Another 6 weeks it will have a foot of ice on the lake and I will be doing 75mph across it on my Arctic Cat!
     
  14. GadgetGuy

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    Everything has its season! :cool:
     
  15. GadgetGuy

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    Same here, except I am flying downhill most of the time...