Solved: IMU calibration. Edited: What is causing the drifting and loss of altitude just after take off?

[Eagledrone]

As of last firmware I seem to have not exactly smooth take offs. Often drifting just after take off and often dropping altitude to as little as a foot off the ground.
I just reviewed the flight logs and it appears the IMU and VPS readings are fairly different.
Then it appears the VPS readings quit completely.

Thoughts?

 

[msinger]

IMU and VPS readings are fairly different

Those values rarely match.

The IMU Altitude is estimated by the barometer in the aircraft. It's the estimated height from the ground at the takeoff point to the aircraft's current altitude. The VPS Altitude is estimated using data from the downward sensors. It's the height from the aircraft's current altitude to the ground below.

 

[Eagledrone]

Those values rarely match.

The IMU Altitude is estimated by the barometer in the aircraft. It's the estimated height from the ground at the takeoff point to the aircraft's current altitude. The VPS Altitude is estimated using data from the downward sensors. It's the height from the aircraft's current altitude to the ground below.

Firstly thank you much for the quick response.
Thanks again for the info. So that wouldn't explain the drifting and altitude drop just after take off.
Otherwise flights seem fine.

 

[msinger]

So that wouldn't explain the drifting and altitude drop just after take off

I'm not able to see that in your screenshot above. Please post the link to your log here.

 

[Mossiback]

Check your Go 4 settings for the downward sensors. Some settings can be reset to default values after update.

 

[Eagledrone]

Here a couple of short flightsView attachment DJIFlightRecord_2018-12-04_[16-29-14].txtView attachment DJIFlightRecord_2018-12-04_[16-29-37].txt

 

[Eagledrone]

Not sure if it helps but here is a longer flight.View attachment DJIFlightRecord_2018-12-04_[16-12-06].txt

 

[Eagledrone]

Check your Go 4 settings for the downward sensors. Some settings can be reset to default values after update.

Thanks I'll check it out.

 

[Eagledrone]

Is it normal to see the IMU have a 10.6' reading at landing?

 

[Hobbo]

Is it normal to see the IMU have a 10.6' reading at landing?

A related query - what happens to the drone’s understanding of its altitude when it flies off a cliff? eg if the max altitude is set at say 50 and its at say 45 feet but then I take it off a cliff which is say 200 feet high. Does it issue a warning that’s its exceeded the max altitude? Does it automatically descend to 50 feet (which would be a problem if I’m standing on top of the cliff?)

 

[DanMan32]

All altitude references are referenced from takeoff altitude, with exception of when in VPS range.

So, if you take off from near a cliff, go up 100', it will show 100'. Now go over that cliff and then go down 200', it will show -100'.

 

[Meta4]

A related query - what happens to the drone’s understanding of its altitude when it flies off a cliff? eg if the max altitude is set at say 50 and its at say 45 feet but then I take it off a cliff which is say 200 feet high. Does it issue a warning that’s its exceeded the max altitude? Does it automatically descend to 50 feet (which would be a problem if I’m standing on top of the cliff?)

If you were designing a drone, would you make it automatically descend a long way because it was flown past a cliff edge?
If you fly your drone out past a cliff edge, your drone has no way to tell it is so far above the ground below.

 

[lolo780]

Is it normal to see the IMU have a 10.6' reading at landing?

How long was your flight?
If the barometer changes, it will throw the altimeter off. Flying at sunrise/sunset really highlights this, so fly with caution.

 

[Eagledrone]

How long was your flight?
If the barometer changes, it will throw the altimeter off. Flying at sunrise/sunset really highlights this, so fly with caution.

38.2 seconds.

 

[Simmo]

 

[Eagledrone]

So my drifting was solved with a IMU calibration. It's back to normal.
Note on the log. The VPS and IMU altitude are almost perfectly in agreement now.

 

[Eagledrone]

Screenshot of the log