Weird problem: Telemetry distance constantly fluctuates

[langcpht]

I've owned a Mavic 2 Pro for about a year. I bought it second-hand and it was flown very little by the previous owner. I've recently noticed a weird issue (maybe not really an issue?) that I'm not sure if I should be concerned about. The telemetry on both the controller and the GO4 app will show the distance traveled and distance to the controller constantly increasing and decreasing, sometimes by hundreds of feet, even if the aircraft hasn't been launched. It usually goes up and down by a few feet every few seconds but it seems wildly inaccurate since I've seen it go as far as 200-something feet just sitting on my desk or in my driveway.

This happens no matter how many satellites I have locked. I've noticed it with 10 or less and as many as 14 satellites. The "distance" will go from 3-4 feet to 200+ and everywhere in between while it just sits there on the ground. It doesn't seem to affect the performance of the aircraft. I've flown it a half dozen times since I noticed this issue, but I do find it very odd and it makes me concerned that it will cause unforeseen problems. I could attach a video or photo/screenshot if it would be of any help. I'm using a Google Pixel 2 running Android 10 and the most recent GO4 if that's of any importance.

Has anybody else noticed this? Should I be concerned? Should I just shut up and fly?

 

[boblui]

If only the distance to the controller is exhibiting this anomality then the phone's GPS may not be working properly.

 

[langcpht]

the GO4 app will show the distance traveled and distance to the controller constantly increasing and decreasing

I quoted my original post here. It's both the distance traveled AND the distance to the controller. The telemetry shows the drone moving sometimes hundreds of feet while it sits still without even taking off. I've just tested it on my bedroom floor. I'm watching the distance traveled and distance to the controller ping-pong by as much as 30 feet. Sometimes it's much more drastic. I attached a photo that shows the aircraft just sitting on the floor with the telemetry showing it's already traveled 20 feet and is 26 feet away from the controller in the same room.



Perhaps I'm being overly paranoid about it, but I just feel as though it shouldn't show ANY movement if the aircraft hasn't even left the ground.

 

[Meta4]

If only the distance to the controller is exhibiting this anomality then the phone's GPS may not be working properly.

The app doesn't use the phone's GPS to calculate distances.
The app calcuclates the difference between the home point and the drone's location, both recorded by the drone's GPS receiver.

 

[boblui]

I quoted my original post here. It's both the distance traveled AND the distance to the controller. The telemetry shows the drone moving sometimes hundreds of feet while it sits still without even taking off. I've just tested it on my bedroom floor. I'm watching the distance traveled and distance to the controller ping-pong by as much as 30 feet. Sometimes it's much more drastic. I attached a photo that shows the aircraft just sitting on the floor with the telemetry showing it's already traveled 20 feet and is 26 feet away from the controller in the same room.

View attachment 106576

Perhaps I'm being overly paranoid about it, but I just feel as though it shouldn't show ANY movement if the aircraft hasn't even left the ground.

If "distance travelled" refers to the display " D 20.7ft" in your screen capture, then the description is inaccurate. That's the straight-line distance from the home point, not distance travelled.

Its also strange that the craft can see as many as 10 GPS satellites in your bedroom.

The only thing I can imagine is that the GPS of the craft has got some problems. It should not be able to return to home accurately.

 

[Meta4]

I attached a photo that shows the aircraft just sitting on the floor with the telemetry showing it's already traveled 20 feet and is 26 feet away from the controller in the same room.

View attachment 106576

Since that demonstration is indoors, it shouldn't be relied on as accurate.
The differences could be explained as being due to the poor quality of GPS reception there.
How is it outdoors with a clear view of most of the sky for good GPS recepton?

 

[boblui]

The app doesn't use the phone's GPS to calculate distances.
The app calcuclates the difference between the home point and the drone's location, both recorded by the drone's GPS receiver.

There are two distance figures displayed on the GO app, one is between the drone and the home point, the other is that between the drone and the controller, the latter can only be computed if the coordinate of the phone is known.

 

[Meta4]

If only the distance to the controller is exhibiting this anomality then the phone's GPS may not be working properly.

Sorry ... I misread your post.
There's good reason not to trust GPS data from either GPS receiver in an indoor situation.

 

[langcpht]

Since that demonstration is indoors, it shouldn't be relied on as accurate.
The differences could be explained as being due to the poor quality of GPS reception there.
How is it outdoors with a clear view of most of the sky for good GPS recepton?

It behaves essentially identically, whether indoors or outdoors. The fluctuations are not consistent, either. Some times It'll drift hundreds of feet, sometimes 10 or less, other times between 20 and 30. Like I said, performance of the aircraft in the air seems predictable and I haven't had any unusual issues in flight, but this behavior makes me worried that something will eventually go wrong.

 

[boblui]

Definitely look not OK to me. Suggest to check two things :

1) open up the map in the GO app, zoom in and observe the location of the craft on the map, does it drift about as the distance figures change ?

2) try doing RTH, does it always land within a few meters from the home point ?

 

[apeel]

Not sure if this will help, but if doubt, I would make sure you recalibrate the IMU and the Compass and then see if the behavior is corrected. And rest assured, if I saw this behavior, I would be concerned as well. Keep digging. Hopefully, someone will have a definitive recommendation for you.

 

[langcpht]

Definitely look not OK to me. Suggest to check two things :

1) open up the map in the GO app, zoom in and observe the location of the craft on the map, does it drift about as the distance figures change ?

2) try doing RTH, does it always land within a few meters from the home point ?

1) The aircraft remains in place when zoomed in on the map.
2) I have only used the RTH feature once since owning it, and it landed within about 2 feet from the takeoff point. I could test this further if it would be of help to troubleshoot.

Not sure if this will help, but if doubt, I would make sure you calibrate the IMU and the Compass and then see if the behavior is corrected. And rest assured, if I saw this behavior, I would be concerned as well. Keep digging. Hopefully, someone will have a definitive recommendation for you.

I recalibrated everything I could using the DJI Assistant on Windows once I noticed this behavior. Nothing has changed. I'm prompted to re-calibrate the compass nearly each time I fly (which is maybe twice a month). It seems to calibrate fine and there are no issues in flight.

 

[boblui]

1) The aircraft remains in place when zoomed in on the map.

That means it's GPS coordinates are not changing. That's in line with the fact that the craft flies OK. The jumping in the distance figures must be due to some kind of software problem of the GO app. Suggest to update to the latest version.

 

[sar104]

This is a lot of speculation that would be cleared up with a look at a flight log.

 

[langcpht]

The jumping in the distance figures must be due to some kind of software problem of the GO app. Suggest to update to the latest version.

My original post clearly mentions that I'm running both the latest Android OS and the latest GO4 release. I appreciate the help, however.

This is a lot of speculation that would be cleared up with a look at a flight log.

Would any flight log do? There isn't any abnormal behavior during flight, it just appears to be what the telemetry is feeding back to me is screwy. I'll upload my last flight if it would be of help.

 

[sar104]

My original post clearly mentions that I'm running both the latest Android OS and the latest GO4 release. I appreciate the help, however.




Would any flight log do? There isn't any abnormal behavior during flight, it just appears to be what the telemetry is feeding back to me is screwy. I'll upload my last flight if it would be of help.

The telemetry is what the app is displaying and recording, so it should be reflected in the log.

 

[langcpht]

Excellent. I'll upload the last flight log when I have the opportunity. It likely won't be for another 4-5 hours so feel free to keep speculating in the meantime. I appreciate everybody taking the time to help out. I'm quite tech savvy, but drones are a whole new thing for me. I competitively raced radio controlled cars for nearly 20 years and never thought I'd be going from surface to sky.

 

[Meta4]

feel free to keep speculating in the meantime.

Much of the speculating has been completely off the mark, with suggestions that have nothing to do with GPS.
Recalibrating compass or IMU won't make any difference as these ate unrelated systems.

You said this happens outdoors but haven't given any details of the outdoor environment where this happens.
Is it a clear area, where the most of the horizon is visible, or is it a cluttered area where the horizon is blocked by trees, buildings or terrain?

 

[langcpht]

You said this happens outdoors but haven't given any details of the outdoor environment where this happens.
Is it a clear area, where the most of the horizon is visible, or is it a cluttered area where the horizon is blocked by trees, buildings or terrain?

I live in a valley in southern Oregon where there are mountains and trees on all sides. The "true" horizon is never visible as there are mountains in every direction, if that's what you're asking. The majority of the flights I make are around bodies of water or wooded areas and I seldom go higher than 100 feet. I can lock 14 satellites in my driveway and 10 inside my house. I've never flown with less than 10.

I'm curious about why the geographical topography would make a difference -- if I have satellites locked in I wouldn't think it would matter what's around me. But again, this is relatively new to me, so I defer to those have knowledge and experience.

 

[Meta4]

I'm curious about why the geographical topography would make a difference -- if I have satellites locked in I wouldn't think it would matter what's around me. But again, this is relatively new to me, so I defer to those have knowledge and experience.

I'm just trying to work through things that might have an effect on your GPS.
Mountains, forest, and buildings block radio signals
GPS reception is varies with the amount of sky that the antenna can "see".
If you have a clear view of 75% of the sky, you should have perfect GPS reception.
If you are in an urban canyon or deep forest with only 10% sky, you have problems.
Up in the air, above obstructions, the drone won't have any problem with GPS.

How much of the sky is visible from your outdoor observation spot?