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Veering right at higher altitudes..

jmark

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Only just noticed this as I recently turned off beginner mode and can now fly faster and higher.

Basically, going full throttle with factory settings in P-mode had my mavic veer slightly to the right at higher altitudes (can't remember exactly how high, but perhaps 50m). It didn't seem to do this at lower ones. I'lI try and get a video of it when I'm out next. It wasn't a particularly windy day, perhaps 2m/s at ground level Is this due to wind or something else?
 

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My first thought was the affect of winds aloft. Winds aloft are different than winds on the ground. The higher you fly, the more affect it has on your flight plan. It might be considered overkill for a drone pilot, but for a full scale pilot, it's standard procedure,

If a drone pilot is considering a long, high altitude mission, it's a good idea to get weather reports via METAR. If your wind is out of the south at 7, you should start your mission heading south, into the wind. If you start north, there's a good chance you will run out of battery before your mission is complete. Plenty of stories on the forum about drones landing short of the take-off point due to high winds.


When I was kid, and my dad and I were going flying, we always looked at the treetops before we even pulled out of the driveway. If the treetops were bending from the wind, we would go back inside and get the weather report from the airport. Dad would ask the FBO, "are you flying today" and we would or would not go depending on what the FBO said.
 
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Dmbrody

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Sounds like you need to do a compass calibration. If that doesn’t fix the issue, then do a stick calibration.
 
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jmark

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My first thought was the affect of winds aloft. Winds aloft are different than winds on the ground. The higher you fly, the more affect it has on your flight plan. It might be considered overkill for a drone pilot, but for a full scale pilot, it's standard procedure,

If a drone pilot is considering a long, high altitude mission, it's a good idea to get weather reports via METAR. If your wind is out of the south at 7, you should start your mission heading south, into the wind. If you start north, there's a good chance you will run out of battery before your mission is complete. Plenty of stories on the forum about drones landing short of the take-off point due to high winds.
Thanks for the tip, but this being my first expensive Drone I tend to be over careful and don't fly if its particularly windy. I also never flu far out, perhaps 350m at most, and make sure I have plenty of power left for the return journey. This will probably change when I become more confident, and I'll definately be careful with flying direction then. I'll try and get up a video of what I mean, let's say the wind was 4m/s at 50 metres up, would this still be enough to effect the flight path of the Drone?
 

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let's say the wind was 4m/s at 50 metres up, would this still be enough to effect the flight path of the Drone?
Yes, absolutely, winds of 4m/s (9mph) will affect your flight path especially if it was a 90° crosswind. Considering the max speed in P mode is 32km/h (20mph), you are dealing with a wind that is almost half of your airspeed.
 
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I will also try this. Although I'm getting no prompts form the Drone to calibrate again.
DJI Go doesnt prompt you to calibrate the controller or give you any type of error message that it's out of calibration, but you can try it and see if it helps.
 
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sar104

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How would I find and post the log file?
The txt log from your mobile device is one option:

DJI Flight Log Viewer - Phantom Help

In cases where heading issues are suspected, the aircraft or mobile device DAT files contain more relevant data:

How to retrieve a V3 .DAT File from the AC

How to retrieve a V3.DAT from the tablet

The aircraft file is harder to find, much larger, and may or may not be accessible (it varies by firmware and aircraft version), so I recommend grabbing the mobile device DAT.
 

Dmbrody

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I will also try this. Although I'm getting no prompts form the Drone to calibrate again.
My money is on the stick calibration.

Edit:
You mentioned going “full throttle,” so my speculation is that the altitude has nothing to do with it. You just haven’t experimented enough at low altitude. When your sticks aren’t properly calibrated, sometimes pushing the stick straight up is interpreted by the controller as up and slightly to one side. Sometimes it isn’t obvious until you go full throttle, which sounds a lot like what you described.
 
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jmark

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So, here is a log to my first flight this morning when testing this. Severe veering to the right when at full throttle in P-mode.

This is the text file..

https://drive.google.com/file/d/ ... G-/view?usp=sharing

This is the DAT file.

18-08-08-09-15-27_FLY048.DAT

Basically, any time the craft is flying in a long straight line on the map, it veers right.

Any help?

I tried recalibrating everything; IMU, compass and controller but it hasn't help.

The following video is from about 2mins into the above flight. The trees were hardly moving so there can't have been that much wind. I had the crosshairs centered dead on the large tree and it the veering was quite substantial at only 12m in height. The craft was virtually flying diagonally. You also see that when I stop the craft shifts to the right slightly. Could this just be wind or it is something to consider returning the Mavic back about?

 

sar104

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So, here is a log to my first flight this morning when testing this. Severe veering to the right when at full throttle in P-mode.

This is the text file..

https://drive.google.com/file/d/ ... G-/view?usp=sharing

This is the DAT file.

18-08-08-09-15-27_FLY048.DAT

Basically, any time the craft is flying in a long straight line on the map, it veers right.

Any help?

I tried recalibrating everything; IMU, compass and controller but it hasn't help.

The following video is from about 2mins into the above flight. The trees were hardly moving so there can't have been that much wind. I had the crosshairs centered dead on the large tree and it the veering was quite substantial at only 12m in height. The craft was virtually flying diagonally. You also see that when I stop the craft shifts to the right slightly. Could this just be wind or it is something to consider returning the Mavic back about?

I'll take a look.
 

Dmbrody

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Have you contacted DJI support?

It still looks like a stick calibration issue to me. I had the same issue (less severe) just 2 weeks ago on a Mavic Air and stick calibration fixed it.

I’m curious how your Mavic handles tap to fly or a simple mission with a straight line.

If @sar104 doesn’t find anything in the logs, then DJI support is really your only option.
 

sar104

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It's the old J-hook maneuver, back from the dead.

Graph1.png

But notice that it doesn't alway hook to the right though - it does that when heading SE but hooks to the left (not as much) on the way back.

So what is causing that. A look at the magnetic and gyro yaw gives a clue. On the way out we get this:

Graph2.png

What you are seeing there is that the computed magnetic yaw changes with pitch (increases with increasing pitch), which it obviously should not. The gyros don't see any rotation. That's also probably why you just noticed - in beginner mode you were not using much pitch, so it's speed, not altitude, that matters.

Looking on the way back the effect is reversed:


Graph3.png

Magnetic yaw decreases with increasing pitch.

Since the IMU computes the magnetic yaw by combining the 3-axis magnetometer data with the attitude computed from the rate gyros and the accelerometers, that could be due to an out-of-calibration compass or IMU, or a hardware issue with the IMU. It doesn't seem obvious whether it is the compass or the IMU causing the problem, but I think should be possible to distinguish those cases by simulating the magnetometer measurements, adding synthetic pitch, and transforming the frame of reference back to earth to calculate the resulting magnetic yaw. Deliberately putting an error into the pitch represents bad IMU attitude data, while putting an error into the magnetometer readings will simulate that option.

Separately, you could try calibrating the compass to see if that fixes it, and then calibrate the IMU if that doesn't work.
 

jmark

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OP is your drone still under warranty?
I've had the drone a week, and over here we get 2 years warranty. I'm also well within their returns policy (which is their 2 months not satisfied policy), so I'm curious as to if I should do that and buy a new Mavic from another retailer so I don't get caught up in warranty claims. I'm really loving this drone, but these problems are really taking away the enjoyment and excitement of owning it.
 
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jmark

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Have you contacted DJI support?

It still looks like a stick calibration issue to me. I had the same issue (less severe) just 2 weeks ago on a Mavic Air and stick calibration fixed it.

I’m curious how your Mavic handles tap to fly or a simple mission with a straight line.

If @sar104 doesn’t find anything in the logs, then DJI support is really your only option.
I will contact them
 

jmark

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It's the old J-hook maneuver, back from the dead.

View attachment 43423

But notice that it doesn't alway hook to the right though - it does that when heading SE but hooks to the left (not as much) on the way back.

So what is causing that. A look at the magnetic and gyro yaw gives a clue. On the way out we get this:

View attachment 43424

What you are seeing there is that the computed magnetic yaw changes with pitch (increases with increasing pitch), which it obviously should not. The gyros don't see any rotation. That's also probably why you just noticed - in beginner mode you were not using much pitch, so it's speed, not altitude, that matters.

Looking on the way back the effect is reversed:


View attachment 43426

Magnetic yaw decreases with increasing pitch.

Since the IMU computes the magnetic yaw by combining the 3-axis magnetometer data with the attitude computed from the rate gyros and the accelerometers, that could be due to an out-of-calibration compass or IMU, or a hardware issue with the IMU. It doesn't seem obvious whether it is the compass or the IMU causing the problem, but I think should be possible to distinguish those cases by simulating the magnetometer measurements, adding synthetic pitch, and transforming the frame of reference back to earth to calculate the resulting magnetic yaw. Deliberately putting an error into the pitch represents bad IMU attitude data, while putting an error into the magnetometer readings will simulate that option.

Separately, you could try calibrating the compass to see if that fixes it, and then calibrate the IMU if that doesn't work.
Wow, thanks for the in-depth reply. Although I'm not entirely sure what it all means. So, should I calibrate EMU again and the compass?

I live over a garage, and the garage is full of scrap metal, power tools and goodness knows what else. Should I maybe calibrate the EMU somewhere else?

I've noticed, when checking camera settings inside, that I get severe compass warnings from the drone when in my living room, above the aforementioned garage. Could there be something in the garage that screws up my EMU calibration? Also, where I normally calibrate my compass is about 5 meters (outside) from the garage. Could this be causing the issue?

PS. Also, there is a train track running to the left of where I live with overhead power lines. Could this have something to do with it? "To the left" would be to the left of where the drone did the J manoeuvre first on the flight path picture you posted above. I also noticed yesterday that the drone flew pretty much bang straight at an alt of about 5 metres at full p-mode speed until it neared the tracks. Today I will take it to a location further away from the tracks and see if I still get the J-hook pattern.

Graph1_edit.jpg

The black line above shows roughly where the tracks lie in relation to the flight path.

PPS: Firmware is up to date to current if that has anything to do with it.
 

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