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Bobbing Action
511 8 2017-1-30
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tvl
lvl.4
Flight distance : 197779 ft
United States
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I have a quick question for those who have experience with the P4. I've only had my drone for two days now and just noticed something new this afternoon that has NOT occurred before while flying. While the craft is hovering roughly 1 to 2 feet off the ground it wants to bob up and down a little. All other times I had flown it it was completely stable while hovering at this height. Have I done something unknowingly OR is there a calibration that needs updating?
2017-1-30
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dronist
Captain
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United States
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No it is normal. If it is too close to the ground it might want to land or not to land. Try to keep it above 3 feet.
2017-1-30
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Punchbuggy
Captain
Flight distance : 395551 ft
Australia
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It may be trying to compensate for a light breeze
2017-1-30
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Nigelbrinkmann
First Officer
Flight distance : 586391 ft
Australia
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Have you been doing this hovering test in the same position (eg same take of point every time) , or on different surfaces? Another thing, check to see if it is stable when you get it up a lot higher?
Maybe calibrate your vision sensors using your PC.
2017-1-30
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tvl
lvl.4
Flight distance : 197779 ft
United States
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I have something I would like to add to my original post which may explain the bobbing motion I encountered today. However, one of the experts on this site will hopefully be able to confirm if my suspicion is correct.

After each flight and during landing for the past two days, I have played around with the craft when it gets very near to the ground (about 1 to 2 feet above the surface of the lawn). Again, it has always hovered steady with almost no moment whatsoever. However, on my last flight today, I wanted to fly it after dark. It was very dark (no moon) and the craft flew beautifully all over the neighborhood and over to the nearby school and back. Once it returned home, I lowered it as always and I wanted to hover it just above the surface of the lawn. That is when I encountered the bobbing action. If I raised it up just a few feet it became very steady and stable. I'm thinking since it was dark, the sensors were having difficulty getting a good view of the ground, which in turn caused the bobbing. Is this a correct assumption or am I totally off base?
2017-1-30
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DJI-Jamie
DJI team
Flight distance : 112405 ft
United States
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Do you have anything blocking the VPS sensors below, like a 3rd party landing gear bracket?
2017-1-30
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Punchbuggy
Captain
Flight distance : 395551 ft
Australia
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tvl Posted at 2017-1-30 21:01
I have something I would like to add to my original post which may explain the bobbing motion I encountered today. However, one of the experts on this site will hopefully be able to confirm if my suspicion is correct.

After each flight and during landing for the past two days, I have played around with the craft when it gets very near to the ground (about 1 to 2 feet above the surface of the lawn). Again, it has always hovered steady with almost no moment whatsoever. However, on my last flight today, I wanted to fly it after dark. It was very dark (no moon) and the craft flew beautifully all over the neighborhood and over to the nearby school and back. Once it returned home, I lowered it as always and I wanted to hover it just above the surface of the lawn. That is when I encountered the bobbing action. If I raised it up just a few feet it became very steady and stable. I'm thinking since it was dark, the sensors were having difficulty getting a good view of the ground, which in turn caused the bobbing. Is this a correct assumption or am I totally off base?

Yes, that's quite a significant add-on of info... :-) It wasn't sure where the ground was (relying on the ultra-sonic, I'd say).
2017-1-30
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Nigelbrinkmann
First Officer
Flight distance : 586391 ft
Australia
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tvl Posted at 2017-1-30 21:01
I have something I would like to add to my original post which may explain the bobbing motion I encountered today. However, one of the experts on this site will hopefully be able to confirm if my suspicion is correct.

After each flight and during landing for the past two days, I have played around with the craft when it gets very near to the ground (about 1 to 2 feet above the surface of the lawn). Again, it has always hovered steady with almost no moment whatsoever. However, on my last flight today, I wanted to fly it after dark. It was very dark (no moon) and the craft flew beautifully all over the neighborhood and over to the nearby school and back. Once it returned home, I lowered it as always and I wanted to hover it just above the surface of the lawn. That is when I encountered the bobbing action. If I raised it up just a few feet it became very steady and stable. I'm thinking since it was dark, the sensors were having difficulty getting a good view of the ground, which in turn caused the bobbing. Is this a correct assumption or am I totally off base?

Hi tvl,
Your assumption is spot on!! this is quite normal operation in your circumstances.   
2017-1-30
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Mike-the-cat
Captain
Flight distance : 14411854 ft
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Singapore
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Normal - the barometric sensor (which helps maintain altitude) gets fluctuating readings if the craft is close to the ground under still conditions because of the downdraft pressurises the air below the craft. If there's a steady breeze, this effect is reduced. Simple physics.  I think when landing, the sensor is turned off and the ultrasonic sensor has priority. That one isn't affected by pressure.
2017-1-31
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