Incorrect Starting Altitude

[Simsbury]

What would cause the altitude to be off?

When the Phantom 4 is sitting on the ground it gives an incorrect altitude. Usually saying it's a couple of feet in the air while it's grounded.

It flies perfectly fine otherwise

 

[Brockrock]

Is this after a flight or upon initial startup prior to a flight?

It is not uncommon for the altitude readout to be off a bit after a flight upon landing at the same Home Point from which it took off. The tolerances are not perfect in that regard.

If this is on initial startup, it should indicate 0', assuming startup occurred while the copter was sitting undisturbed. I would do a fresh IMU calibration on a perfectly level surface as the first step. If this does not correct the issue, I would then do a firmware refresh followed by another IMU calibration. These steps can actually correct many of the odd glitches that occur from time to time. Kepp us posted.

 

[commodon]

What would cause the altitude to be off?

When the Phantom 4 is sitting on the ground it gives an incorrect altitude. Usually saying it's a couple of feet in the air while it's grounded.

It flies perfectly fine otherwise

My understanding of its ability to discern vertical height is the result of barometric pressure combined with the Vertical Position Sensors (VPS). Hence, when the drone is on the ground it is possible it might display an incorrect height, but this can be overlooked. However, once it takes off and assuming VPS is enabled, the height displayed for VPS is "on the money" up to 30 feet. And once above thirty feet, the VPS is disabled and the height is calculated based on barometric pressure, which can normally be off by a few feet.

Note it is possible the IMU might be out of calibration, but this is generally not something that has to be done unless you've upgraded the firmware. Additionally note the IMU is responsible for maintaining stability during flight, to prevent drift and ensure a level horizon only.

 

[Simsbury]

Thank you for the replies. I've done the IMU calibration but it still occurs. It flies fine - maybe just "one of those things"

 

[Duchunter]

Do you have anything blocking the sonar like a gimbal guard or some type of attachment to the legs?