Altitude Reading Issues

[bkushner]

I'm getting a bad altitude readout when flying the M3. During the flight my altitude starts to go into the negative range. For instance I could be at 12 foot and it says -8 feet. There is a video of a Chinese tested flying the drone before it came out and it's showing the same issue. Negative height...Anyone else seeing this?

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[adcimagery]

It's altitude relative to takeoff point. I've not watched the video, but are you flying from a high starting point to a lower point?

 

[Meta4]

I'm getting a bad altitude readout when flying the M3. During the flight my altitude starts to go into the negative range. For instance I could be at 12 foot and it says -8 feet. There is a video of a Chinese tested flying the drone before it came out and it's showing the same issue.

I know you've been flying long enough to understand when your drone is actually flying at negative height, so I won't suggest that.

A small error in indicated height is common over the duration of a flight.
If you consistently see differences of >20 ft, the first thing I'd do is an IMU calibration to see if that brings things back to a more accurate range.

 

[Meta4]

There is a video of a Chinese tested flying the drone before it came out and it's showing the same issue. Negative height..

The video guy has no idea what he's talking about.
The car in the video is going down a hill so it's completely normal that it should show negative height.

Then at 3:40 he starts up with the same uninformed, alarmist stuff that was going around about the Air 2s a little while back.
This was just because some folks don't understand that some drift is completely normal with a barometric sensor and despite his concerns, it isn't a major problem at all.

 

[bkushner]

I know you've been flying long enough to understand when your drone is actually flying at negative height, so I won't suggest that.

A small error in indicated height is common over the duration of a flight.
If you consistently see differences of >20 ft, the first thing I'd do is an IMU calibration to see if that brings things back to a more accurate range.

I've been flying long enough to never have seen this issue in any of my drones before. It's a noticable problem when flying over water because I don't have an accurate reading. Again, I've had about 2,000 flights on my flight plan alone and never have seen this since 2016 when I started flying. First thing I did was an IMU and it's done nothing. Here is data from one of my recent flights....thoughts?

 

[Meta4]

Here is data from one of my recent flights....thoughts?

It would be a lot more helpful if you post actual data rather than a screenshot of part of an Airdata summary?

 

[bkushner]

It would be a lot more helpful if you post actual data rather than a screenshot of part of an Airdata summary?

Well I was just showing you. It seems clear your upset that I've reported this issue..My apologies..

 

[bkushner]

It's altitude relative to takeoff point. I've not watched the video, but are you flying from a high starting point to a lower point?

I take off and land at the same spot. When the drone is about 5 foot off ground from landing it says -85ft.

 

[Meta4]

Well I was just showing you. It seems clear your upset that I've reported this issue..My apologies..

I'm not upset.
I can't tell much from a listing of various altitudes without some more information to understand what's going on.
I need to see the corresponding joystick inputs.

 

[bkushner]

I'm not upset.
I can't tell much from a listing of various altitudes without some more information to understand what's going on.
I need to see the corresponding joystick inputs.

I will work on getting the record.

 

[Meta4]

I will work on getting the record.

The url of the airdata report would be fine or the .txt file that the Airdata report is based on.

 

[Dave Maine]

This has been discussed well many times. The drones use a barometric altimeter that is set to 0 on takeoff. All heights will be relative to takeoff 0 point.

In addition, the barometric sensor, probably for cost reasons, is not very accurate.

In addition, the barometric condition of the earth’s atmosphere vary over time, causing shifting readings even with highly accurate barometers.

 

[bkushner]

This has been discussed well many times. The drones use a barometric altimeter that is set to 0 on takeoff. All heights will be relative to takeoff 0 point.

In addition, the barometric sensor, probably for cost reasons, is not very accurate.

In addition, the barometric condition of the earth’s atmosphere vary over time, causing shifting readings even with highly accurate barometers.

So your saying when my drone lands at -85 feet from where it took off this is normal? When the whole flight is showing 15 feet when I'm at 100?

 

[sar104]

So your saying when my drone lands at -85 feet from where it took off this is normal? When the whole flight is showing 15 feet when I'm at 100?

That sounds like a problem. However, as @Meta4 said above, without a log file it's hard to draw any firm conclusions.

 

[bkushner]

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

 

[Dave Maine]

Seems extreme, but what sar104 suggests is right. Send logs. My personal experience with 3 different DJI drone types, is that large an error is very large, but not out of the possibility. Try the same flight in the same spot, on 3 different days and see what happens.

 

[bkushner]

That sounds like a problem. However, as @Meta4 said above, without a log file it's hard to draw any firm conclusions.

Posted

 

[Meta4]

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

The indicated height has drifted 50 ft over 25 minutes in one flight and 80 ft in a 19 minute flight.
VPS height also drifted, but not as much.
It showed 0 ft at launch but 5-6 ft when the drone lands.
The errors in indicated height are excessive and a problem.

I don't see any appreciable change for the short periods where you aren't varying the real height of the drone.
It would be interesting to see the data from a flight where you maintained steady altitude for 10 minutes.

There's also something weird going on with the speed data shown in the csv file.
It shows unbelievable numbers and speed changes, but the speed data in the log viewer display looks normal.

 

[bkushner]

This continues on every flight so far. Support request in...waiting to hear back.