False Altitude

Uke0755 · Mar 11, 2016

Recently (about 2 weeks ago) I noted my P3 Standard was showing an altitude of 35 feet when in reality it was approximately 10 feet above the ground. After the flight and back at home, I tried to sync my flight log numerous times with each failing to upload. They did eventually but it keeps recurring. I have followed the same pre flight checks as always, I have the latest firmware, and I have not changed anything major in or on my P3. Any help is greatly appreciated.

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Meta4 · Mar 12, 2016

Uke0755 said:
Recently (about 2 weeks ago) I noted my P3 Standard was showing an altitude of 35 feet when in reality it was approximately 10 feet above the ground.

The first thing to check is to get a good level surface and recalibrate your IMU.
That often fixes aititude errors.

Uke0755 · Mar 13, 2016

Thanks! I will try that again.

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With The Birds · Mar 13, 2016

As mentioned... IMU cal can help. Usually where you have a big variation between flying temp and the temp at time of calibration.

Uke0755 · Mar 20, 2016

I've calibrated the IMU numerous times and it is still showing an incorrect altitude...thoughts?

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msinger · Mar 20, 2016

How far is your altitude off?

MedinaTaylor · Mar 20, 2016

Mine used to always be off by 30 to 50 feet. After I did a cold IMU calibration it is never off by more than 10 or 15 feet

Uke0755 · Mar 20, 2016

msinger I had it about 10 feet off the ground near the home point and it showed 24 feet.

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With The Birds · Mar 20, 2016

My personal experience only. Cold IMU calibration (placing phantom in fridge) prior to imu cal gave me alt readings towards end of flight that were consistently higher than actual. This does not seem to make sense as i would have expected internal temp reference for correction of barometer. The problem went away when i did a new cal closer to ambient temp though.

CactusJackSlade · Mar 21, 2016

Many, threads on this.... might try the search function on this forum... or on Google, I found 5 threads on Google that linked right back here on Phantom Pilots.

Imabiggles · Mar 23, 2016

With The Birds said:
My personal experience only. Cold IMU calibration (placing phantom in fridge) prior to imu cal gave me alt readings towards end of flight that were consistently higher than actual. This does not seem to make sense as i would have expected internal temp reference for correction of barometer. The problem went away when i did a new cal closer to ambient temp though.

? fridge cal?

The altitude sensor is simply a barometer - it can be off for many reasons including temp flux, weather moving in, wind, geese farts and space monkeys. Dont worry about it, this is common to all P3s. If you are flying a mission, just make sure you have +20 feet in addition to the highest point on path.