Alltitude not accurate

wutangdaddy · Jun 4, 2017

Good morning....the altitude on my p4 is very inaccurate. It starts off ok on take off....I'm not flying in much wind....and not taking it too high. Is it true that height is measured by the barometer,if so can this be in accurate if there is wind. My main flying spot is over an estuary at the the mouth of a river when the tide is out..... usually just before sunset.

Meta4 · Jun 4, 2017

wutangdaddy said:
Good morning....the altitude on my p4 is very inaccurate. It starts off ok on take off....I'm not flying in much wind....and not taking it too high. Is it true that height is measured by the barometer,if so can this be in accurate if there is wind. My main flying spot is over an estuary at the the mouth of a river when the tide is out..... usually just before sunset.

Wind won't make any difference. Even on a perfectly calm day, if you're flying the effect on the sensors is the same anyway.
It's common for the altitude reading to be a few feet out over the time of a flight but if it's very inaccurate try recalibrating the IM.

Richard R · Jun 4, 2017

Wind will have virtually no effect on your altitude sensor. While the physicist part of me wants to talk about the Bernouli effect. In practical terms, it wouldnt cause any significant change in the pressure sensed by the variable resistor on the circuit board. What makes you think that the accuracy is off? Your comment seems o imply that the altitude reading is drifting with time. And remember, the height reported is the height above the takeoff point not actual height above the ground (AGL) directly belowcthecbid.

TheoP · Jun 4, 2017

I tested this yesterday with a laser distance measurement tool mounted on a tripod facing directly up. I could fly the P4P on to the measurement crosshair on the camera and compare the height reported on the controller with the laser measurement. P4P was on 30m and laser reported 28m. I will probably do more measurements later but now I'm working with a 10% error assumption.

With The Birds · Jun 4, 2017

I have seen altitude errors on the P3 of 5 meters with the first pack flown (after 15min flight it was reporting 5m when just about on the ground where I took off). Subsequent packs flown in the same outing didn't have this apparent error. An IMU recal in temp closer to actual ambient for the times flown seemed to correct this issue, a further benefit being a greatly reduced warm up time. A 2m difference is nothing to worry about, allow a few extra metres for safety and all will be good.