Altitude problems

[leng-man_]

Hi guys first of all when in my backyard cycling a battery I noticed the altitude reading was in accurate

To cycle the next battery I left it idling inside the entrance hall in my house didn't take off and the altitude kept going down and down,

I then hovered in atti mode which again have a reading of 2.4m even though I must of been 0.3m off the ground and then it would just sink to the floor and not hold steady, I thought this may be because of the carpet so tried on laminate and the same thing happened,

Any ideas, Liam

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[Mark The Droner]

The altitude reading is not particularly accurate regardless of what aircraft you might have. It's meant to give you a general idea. Hope this helps.

 

[leng-man_]

Oh ok mate it seems better at height

Is it normal for it to descend lower and lower when stationary and not taking off?

Thanks again Liam


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[Mark The Droner]

It's normal for it to do lots of different stuff. I understand your concern. I used to fret about this too when I started, because I wanted everything to be perfect. But altitude readings are not perfect.

I wouldn't worry about it too much unless it was consistently off by a lot.

My pleasure.

 

[Darknezz]

What I have noticed in my phantom 4 regarding tha altitude is this. I m living at the 6th floor of a building. I took off my P4 from the roof and what i noticed is that it counts the altitide from where it has been taken off. So i put the drone 5 meters over the roof and then move it over the road. Altitude was not changed. It continues to show 5 meters although the real distance from ground (road) was about 25 meters. Is this normal ?

 

[Mark The Droner]

Yes. The word "altitude" is misleading. A better way to put it would be "Height From Launch Point."

Hope this helps.

 

[Darknezz]

however this might create unusual situtations especially when you are not flying in a flat level area. By saying that, i m thinking that there is no real altitude metering but rather a mathmetical algorithm which using as base point the launch point instead.

 

[leng-man_]

Yes guys but my problem is if I power up the bird from the launch point the height goes down if I leave it on the ground running

I understand the craft sets this as the starting altitude and not the actual above sea level altitude but surely if I'm not actually taking off or descending it should stay at the zero? Should I video this for you guys?


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[Darknezz]

Have you tried to do again an IMU calibration ? DJI suggest to do IMU calibration every time after firmware update.

 

[chris digata]

your not flying so dont worry, it also works on air density that can be adjusted by temp so will make self adjustments.
its a known problem with p4`s and it will also drop around 10ft when it stops on a straight run, just keep your eye on it and hopefully DJI can adjust something in firmware soon.. but we put up with it for now

 

[leng-man_]

Yeh everything has been re calibrated including imu

Chris I think your right maybe it's to do with the draft below when running might be an idea just to power it on and see what happens

Liam


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[leng-man_]

I've seen a guy in Germany be told by DJI it's a bad IMU sensor so needs changing out


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[RémyHeli]

leng-man_, in your video we can see the ground looks made of material that can be light reflective as well not sure the shapes are allowing clear analysis. This can maybe confuse a little the 2 below cameras.

Probably not directly related to the altitude problem but risk of adding more issues to your test.




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[leng-man_]

So in the real world what surface will vps work over because I've seen many videos where people hover the drone over grass and laminate flooring?


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[RémyHeli]

Some examples: repetitive or lack of patterns/texture, monochrome (ie snow), reflective, moving ground (ie water), transparent, missing/too much light, sonar soundwaves altered (high speed, absorbed (ie carpet), deviated (ie angle), sensors dirty/damaged, other ultrasonic device near operation (ie pest repellent around 40khz)


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[RémyHeli]

Note it's possible to recalibrate VPS with dji assistant software, not needed usually but available.
Would say if issue persists after all kind of calibrations done correctly with latest firmware, open area without metal and power lines, (vps, cold IMU etc.) then you might consider possible hardware fault and submit case with DJI support possibly with video showing behavior and not inside a building (possible extra factors)


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[leng-man_]

Ok thanks for the advice remy!

What surface would you suggest I try it out on?

It's funny you mention the vps because this is my second craft and it asked me to calibrate the vps when I had it the first did not

Liam


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[Darknezz]

From what I have seen, the altitude is not the real altitude between drone and surface under it, but rather the altitude from the point you take off your drone. For example lets suppose you are in a roof a 10 levels building and you take off the drone. You get it up 10 meters from the roof. Altitude show 10m.. Then you move in horizontally over the road. Altitude still shows 10m but now the distance between drone and earth (road) is 40m. This, makes me think that there is no real metering sensor.

 

[N017RW]

This, makes me think that there is no real metering sensor.

You are correct in your example and conclusion.

It's only a barometer and is subject to ambient condition changes as well as it's 'quality' and other implementation considerations.

 

[leng-man_]

Hi guys I know this, the point is if I take off from 0 got to ten meters and hover then back down sometimes I get a reading of -1.1m or more and I am not lower then the take off point


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