Altitude descending (descending) when level on ground

[rabrol]

Hi All.

New Q500 4K owner here (actually new drone user!). Bought the unit used with only 3 previous flights.
Took it out for a spin this morning and noticed the altitude readout was incorrect. It was showing about -45ft when on the ground. This number continually decreased, down to -65ft the last time I looked at the reading, following a subsequent landing.

I performed a compass and accelerometer calibration this afternoon. Then powered up, left the quad sitting on level ground in my back yard. It started at 0.4ft, then continued working its way down over the next few seconds. I turned it off when it got to -4ft after a couple of minutes.

I would imagine this is an accelerometer issue. Is that correct? Or could it be an incorrectly aligned compass?

Aside from not being able to trust the altitude readout, are there any other potential problems this would cause? I noticed it was very slow to descend for landing. Is that because it thinks it is below level ground? What would happen on RTH?

Thanks for your help folks!

 

[Rayray]

May not be a problem. Mine usually is within several feet + or - at startup, then varies during the flight. That reading is inherently imprecise, you got it close when you calibrated.

 

[rabrol]

May not be a problem. Mine usually is within several feet + or - at startup, then varies during the flight. That reading is inherently imprecise, you got it close when you calibrated.

Yes, it came close when calibrated.
After a 15 minute flight this evening, it registered ground level at -65ft! Something doesn't seem quite right...

 

[Ari]

Yes, it came close when calibrated.
After a 15 minute flight this evening, it registered ground level at -65ft! Something doesn't seem quite right...

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[Steve Carr]

Yes, it came close when calibrated.
After a 15 minute flight this evening, it registered ground level at -65ft! Something doesn't seem quite right...

The altitude reading is from an internal barometer which is used as an altimeter. Because these use barometric pressure to calculate altitude they are not known for accuracy. They are also affected by changes in temperature.
Each time you boot up the Q500 it is supposed to calibrate the altimeter close to zero. I understand that during flight GPS is also calculating altitude. Neither is very accurate.
Try booting up the Q and let it sit for about 5 minutes. Then turn it off and restart it to see if it becomes more accurate.

 

[rabrol]

Try booting up the Q and let it sit for about 5 minutes. Then turn it off and restart it to see if it becomes more accurate.

I'll certainly give that a try at the next flight (hopefully this evening). Would be nice if it stablilized and I could use it as a rough guide to altitude.

Is there a way to set the ST10+ to display altitude only from the barometer or the GPS fix?

 

[Steve Carr]

I'll certainly give that a try at the next flight (hopefully this evening). Would be nice if it stablilized and I could use it as a rough guide to altitude.

Is there a way to set the ST10+ to display altitude only from the barometer or the GPS fix?

I have not seen a way to change that. Actually most of the pilots I have talked to don't pay much attention to the altitude reading except for an estimate when they are over 2-300'. That is what I do as well. I prefer to use visual orientation because I fly in steeper terrain where altitude doesn't mean much.

 

[Robear]

I'll certainly give that a try at the next flight (hopefully this evening). Would be nice if it stablilized and I could use it as a rough guide to altitude.

Is there a way to set the ST10+ to display altitude only from the barometer or the GPS fix?

I am having the issue ever since I let Yuneec USA repair my Q500 4k. They replaced the GPS module for a problem that had nothing to do with the problems I reported and now I am dealing with this problem but that is another story. In the meantime, now I can be hovering 20 -30 ft and the ST10+ reports it is -11ft or more below the ground. I get the same results when the Q500 is sitting on the ground. Did you try the suggestion that Steve said and did it work? I haven't had the chance to try it myself due to the recent weather. If this doesn't work I think I will send my Q500 to Aces Deals for repair. Even though my unit is still under warranty, I would rather pay someone I could trust before I let those tech wannabes in Cal. touch it again.