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How high to avoid downdraft affecting the water?
459 8 2018-2-26
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Nigel_
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Just wondering how high you need to fly above water to avoid creating ripples and spoiling the reflections?

Was watching the video from my last flight and thought it would be useful to know in case we get a windless day, the video didn't answer the question though:


2018-2-26
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DEUCEDOG
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Nice video ,  good question about the down draft all i could suggest is hover higher and descend until you create a ripple ?
2018-2-26
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RicardoGray
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DEUCEDOG Posted at 2018-2-26 13:12
Nice video ,  good question about the down draft all i could suggest is hover higher and descend until you create a ripple ?

That's what I'm thinking too. I fly over water a lot, but not real close. I think the closest I've been was around 6-ft over it, but no problems. You have to be aware though in case it wants to drop in altitude. I would think that 10'-15' would be high enough to avoid ripples. Guess you'll just have to try it.
2018-2-26
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dorbot
Second Officer
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France
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Just fly really fast and really close to the water. What could possibly go wrong?
2018-2-26
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Nigel_
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DEUCEDOG Posted at 2018-2-26 13:12
Nice video ,  good question about the down draft all i could suggest is hover higher and descend until you create a ripple ?

The problem with trying it is that once you have created ripples you have to wait ages for the surface to be mirror flat again, and by then the battery will be empty!
2018-2-26
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DJI Susan
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Great job! I'd suggest flying above the water more than 10 meters. Safe flying!
2018-2-26
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Cetacean
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Nigel_ Posted at 2018-2-26 15:08
The problem with trying it is that once you have created ripples you have to wait ages for the surface to be mirror flat again, and by then the battery will be empty!

Aloha Nigel,

     The answer is in with the posts.  For your P4, you will have to test to see what height you have to stay above.  As Susan says, stay above 10 meters.  But, if you go lower, the VPS will kick in for the P4 Series.  The VPS readout gives you a secondary (and more accurate) altitude reading starting at 30 feet.  I have not tested for ripples at thirty feet yet, but I doubt that the downdraft will cause ripples at thirty feet.  I do not get thin grass movement from my downdraft until 15-20 feet and that altitude may or may not cause ripples.  This means you should get a good readout for altitude.

     With your camera facing directly down you will see the reflection of your P4.  Any ripples will distort that reflection.  For the conditions on the day you want to get the shot, test the altitude in an area you will not be using for the shot.  Once you get your altitude go to the site you want to shoot and do it.

     If you are moving forward with camera facing forward, you can fly closer to the glassy water without seeing ripples because you will be constantly flying over clam water.  The smaller the waves / ripples are, the faster the wave propagation dies out so you can fly over the same area more often than you might think.  You can also land to wait it out but use a fresh battery when you fly again, so time your batteries well.  Over water is a bad time for battery issues.

     Hope this helps!

Aloha and Drone On!
2018-2-27
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Crazyio
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Flight distance : 77415 ft

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Sorry but what is the problem flying above the sea in less than 10 meters?
I fly very often above the sea and allways in gps mode. Some of my flights are about 5m above the sea.
Is that dangerous and why?
Thanks a lot
2018-2-27
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RicardoGray
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Crazyio Posted at 2018-2-27 05:06
Sorry but what is the problem flying above the sea in less than 10 meters?
I fly very often above the sea and allways in gps mode. Some of my flights are about 5m above the sea.
Is that dangerous and why?

Nothing at all, as long as that is where it stays. Sometimes I have noticed when flying over the water my Phantom will drift a bit up and down. Even with VPS off. Either way the closer you are, the less time you have to react if something goes south. It is sometimes hard to see through the app just how close it is and if it is wavering any. Even though your altimeter might show it is maintaining perfect altitude, I'm not totally convinced it is 100% accurate/or exactly how close it is to the actual height............within 6", 12", 18"????  So, everything is fine until it dips into the sea. It is like anything, the risk factor goes up the closer you get to the surface. No guarantees here. I guess it is only dangerous if you lose you aircraft.
2018-2-28
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