Phantom 2 (non vision) Altitude Drop

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On my P2 with Zen H3-3D running FW 3.14 SW 3.08, I am finding that at an Altitude of 8 feet or less the copter does not want to maintain Altitude. In GPS Mode and hovering at an Altitude of around 8 feet, it starts descending and doesn't try to maintain Altitude. I can apply some throttle and it will rise but as soon as I release the stick, it starts dropping slowly.

Is this common for the P2?
 
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My FC40 never used to do that, but now it does something similar. I'm thinking my GPS shielding is the cause.
 
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GPS has nothing to do with the altitude. The altitude is measured by a barometric pressure sensor, so if the wind is gusty it can change the altitude during a hover. You may also want to adjust your altitude gain in the assistant program.
 
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GPS has nothing to do with the altitude. The altitude is measured by a barometric pressure sensor, so if the wind is gusty it can change the altitude during a hover. You may also want to adjust your altitude gain in the assistant program.

I tried bumping up the Altitude Gains.First I bumped it 10% then 20% and it didn't help.
 
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On my P2 with Zen H3-3D running FW 3.14 SW 3.08, I am finding that at an Altitude of 8 feet or less the copter does not want to maintain Altitude. In GPS Mode and hovering at an Altitude of around 8 feet, it starts descending and doesn't try to maintain Altitude. I can apply some throttle and it will rise but as soon as I release the stick, it starts dropping slowly.

Is this common for the P2?


I fly sometimes in 15 to 25 mph winds which are typically gusty.

Was there a gusty wind when your bird descended from 8 feet?

Maybe a high pressure area was moving in really fast and it fooled the bird. <--That's a joke:p
 
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No Wind. It does it every time with or without wind. It has been doing this with past FW's also. Where is the Barometer located? I'm guessing inside the FC.
 
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No Wind. It does it every time with or without wind. It has been doing this with past FW's also. Where is the Barometer located? I'm guessing inside the FC.

It's in the NAZA and I don't think it's a barometer in the typical sense of the word. Personally I think steve is wrong. Can you picture an altimeter in the phantom which is capable of measuring altitude to the inch? Now 10 or 12 satellites, that sounds a bit more feasible to me. I've been wrong quite a bit lately, so keep that in mind.
 
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GPS altitude is pretty inaccurate to be honest... It's typically 1.5 times the horizontal accuracy. So at best accurate to 3 or 4 meters... which is fine if it's in a plane at 30,000 feet, but no good close to the ground. Hence the altitude barometer inside the NAZA. The Flytrex also has one, inside a little metal can with a pin hole in it.

upload_2015-5-8_9-39-20.png


Like any barometer, it needs a baseline to zero itself and it does this at power up so it knows where the ground pressure is... as you ascend the pressure drops in a linear fashion so it can work out the height, it also takes into account the temperature...

I used a similar system when launching balloons for the met office down in the Falklands.. way back in another life!
 
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When testing my P2 in the backyard the altitude will drift up and down about 2 feet due to winds moving around the buildings from different directions. Out in an open field that isn't a problem.
 

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