Nearly lost my Mavic Air this morning - Home Point changed randomly

[Simmo]

@Bondaneka Do you recall exactly what you did to initiate RTH?

 

[MavicCF]

@Bondaneka Do you recall exactly what you did to initiate RTH?

@Simmo, you look different!

 

[msinger]

If I recall correctly, there have been numerous issues in the past, especially under Android, with mobile device GPS data and the Go app, even when other apps clearly reported good GPS location data. I thought that was resolved in a previous app update.

There was an issue in the Android version of DJI GO 3.1.2 that would allow the home point to be set to a bogus location when tapping "Current Position" at this prompt:




In the OP's case, the home point was correctly set to the mobile device's current location (instead of a bogus location). The OP said he did not manually reset the home point and that prompt was not displayed, so I'm not sure how he managed to reset the home point. I've never seen anything like this before.

 

[sar104]

There was an issue in the Android version of DJI GO 3.1.2 that would allow the home point to be set to a bogus location when tapping "Current Position" at this prompt:

View attachment 34510


In the OP's case, the home point was correctly set to the mobile device's current location (instead of a bogus location). The OP said he did not manually reset the home point and that prompt was not displayed, so I'm not sure how he managed to reset the home point. I've never seen anything like this before.

It was a bogus location in the sense that the recorded app GPS location was moving around significantly during the flight and so the HP was reset to a location 190 m away from the actual mobile device location. Whether that was due to the phone GPS data jumping around, or just the app location data, I'm not sure.

As for what caused the HP reset in the first place, I agree that is currently a mystery. There's no way for that to happen spontaneously that I can think of, so my guess is that the OP must have triggered it without realizing or remembering.

 

[msinger]

It was a bogus location in the sense that the recorded app GPS location was moving around significantly during the flight

By not being bogus, I meant DJI GO did not set the home point to a seemingly random location (like in DJI GO 3.1.2). The used location (accurate or not) was the location from the flight log.

my guess is that the OP must have triggered it without realizing or remembering.

That's what I'm thinking. The OP either missed us asking him three times now or he's dodging the question.

 

[sar104]

By not being bogus, I meant DJI GO did not set the home point to a seemingly random location (like in DJI GO 3.1.2). The used location (accurate or not) was the location from the flight log.


That's what I'm thinking. The OP either missed us asking him three times now or he's dodging the question.

OK yes - not bogus in that sense. The OP did seem to ignore your specific question on what happened.

 

[Verizondrone28]

Just finished reading through this and wanted to say thank you to all of the experts out here who are willing to jump in and help another drone pilot when things go awry. My first drone is the Mavic Air so I’ve only had it less than 2 months but have learned a ton from this forum. Flight pre-checks, actually reading the manual and understanding all that the drone can do, and above all, actually praciticing in safe areas - not just flying wherever I want. I feel like I’ve learned a ton in the past 2 months and hope to never have to post on this forum that I lost my Air. I still have lots to learn so I’ll keep soaking it up. Thank you!

 

[Bondaneka]

Sorry not to have responded sooner. In answer to the question "Do you recall exactly what you did to initiate RTH?" - Yes, I tapped the RTH icon on the screen - nothing more. I absolutely did not see the "Select Return Position" message shown in the screenshot above.

 

[sar104]

Sorry not to have responded sooner. In answer to the question "Do you recall exactly what you did to initiate RTH?" - Yes, I tapped the RTH icon on the screen - nothing more. I absolutely did not see the "Select Return Position" message shown in the screenshot above.

It's very difficult to find an explanation consistent with that. The home point is not reset randomly without user interaction - in fact I've never heard of that happening. The mobile device DAT file event log might give more information on how the reset occurred if you are interested in trying to chase this down.

How to retrieve a V3.DAT from the tablet

 

[Bondaneka]

Thanks, I will look at your link. The key thing is that I didn't move from the launch point and, other than passing it without knowing the drone was hovering over it when I was chasing after it in my car, I was nowhere near the 2nd home point which was several hundred yards out of the park and in the front garden of someone's house! I have now altered the location settings on my phone to GPS Only, disabling the contribution made by both Wi-Fi and Mobile Network Location on the assumption that when using the phone with the controller, relying on GPS alone to set the home point location will prevent this situation from arising again. Is my thinking on this sound? Any thoughts on this would be most welcome.

 

[sar104]

Thanks, I will look at your link. The key thing is that I didn't move from the launch point and, other than passing it without knowing the drone was hovering over it when I was chasing after it in my car, I was nowhere near the 2nd home point which was several hundred yards out of the park and in the front garden of someone's house! I have now altered the location settings on my phone to GPS Only, disabling the contribution made by both Wi-Fi and Mobile Network Location on the assumption that when using the phone with the controller, relying on GPS alone to set the home point location will prevent this situation from arising again. Is my thinking on this sound? Any thoughts on this would be most welcome.

Yes - that may help prevent inaccurate location data being used, but doesn't answer the question of why the home point was reset.

 

[Travisimo]

Thanks, I will look at your link. The key thing is that I didn't move from the launch point and, other than passing it without knowing the drone was hovering over it when I was chasing after it in my car, I was nowhere near the 2nd home point which was several hundred yards out of the park and in the front garden of someone's house! I have now altered the location settings on my phone to GPS Only, disabling the contribution made by both Wi-Fi and Mobile Network Location on the assumption that when using the phone with the controller, relying on GPS alone to set the home point location will prevent this situation from arising again. Is my thinking on this sound? Any thoughts on this would be most welcome.

I'm trying to understand exactly how the home point is set to avoid a situation like this. At the time of take-off, the home point is set on the aircraft itself, right? And if you verify on the map that the home point is where you are taking off, the home point should never change to something else without user interaction. If a pilot does change the home point during flight to where the controller is location, it uses the mobile device's GPS location, correct? So I assume that if you are using a mobile device that does not have GPS in it, then there is no option to change the home point during flight? So to avoid a situation like this occurring, could you not disable GPS (or at least deny the DJI Go app access to GPS) so that this could not happen? Of course, without GPS location on the mobile device, then you wouldn't be able to see your position on the map, etc right? Just trying to wrap my head around this.

I'm just always trying to logically determine how to avoid situations that I am reading about, and this one baffles my mind. Are we basically down to 1) pilot did reset the home point inadvertently or 2) aircraft did choose a home point on its own based on a spurious GPS location on the mobile device?

 

[MavicCF]

I'm trying to understand exactly how the home point is set to avoid a situation like this. At the time of take-off, the home point is set on the aircraft itself, right? And if you verify on the map that the home point is where you are taking off, the home point should never change to something else without user interaction. If a pilot does change the home point during flight to where the controller is location, it uses the mobile device's GPS location, correct? So I assume that if you are using a mobile device that does not have GPS in it, then there is no option to change the home point during flight? So to avoid a situation like this occurring, could you not disable GPS (or at least deny the DJI Go app access to GPS) so that this could not happen? Of course, without GPS location on the mobile device, then you wouldn't be able to see your position on the map, etc right? Just trying to wrap my head around this.

I'm just always trying to logically determine how to avoid situations that I am reading about, and this one baffles my mind. Are we basically down to 1) pilot did reset the home point inadvertently or 2) aircraft did choose a home point on its own based on a spurious GPS location on the mobile device?

To my knowledge all you said is correct.
The most likely option at this point seems to be that pilot inadvertently reset the home point (see @msinger's post #43) to the mobile device's location which was way off from where it should have been. To quote everyone else, do you remember at all how you initiated RTH?

 

[sar104]

To my knowledge all you said is correct.
The most likely option at this point seems to be that pilot inadvertently reset the home point (see @msinger's post #43) to the mobile device's location which was way off from where it should have been. To quote everyone else, do you remember at all how you initiated RTH?

See post #48.

 

[dragonmuzz]

I've always flown all my DJI drones with smartphone GPS/data and WiFi all off and as yet I've never had a problem ...never had a RTH issue ever

 

[MavicCF]

See post #48.

Sorry, hadn’t reloaded the page in a while. So will it remain a mystery?

 

[bugman]

While flying the Mavic air at a distance of 3000-4000 ft I started losing signal and control. The controls were very difficult--I'd tell the drone to yaw and it would after a couple of seconds and it was an over corrected yaw. I was just trying to head back. So I initiated a return to home from the app and the drone started heading the wrong way for a 50 ft or so before I pressed the pause button. I started walking toward it to get better signal and playing with antenna till I was able to turn it toward home (which was correct on map). Then I brought it home manually. This has happened a couple of times already. I don't trust the return to home anymore and I try to limit my flights distance to 2500 ft to avoid all these issues. I'm afraid that if I lose signal it will be a goner.

 

[sar104]

Sorry, hadn’t reloaded the page in a while. So will it remain a mystery?

The OP is going to try to get the mobile device DAT file. The log in that may shed some light on events.

 

[Jameslavis]

My thoughts went right to the phone location reporting as well. I typically fly In airplane mode just to control what the app and my phone say to each other. It would be different if I wanted to reset my HP tho. If I was the OP, I’d be shutting cell comms down.

 

[msinger]

If I was the OP, I’d be shutting cell comms down.

That really shouldn't be necessary since the home point doesn't accidentally reset itself. There is either a bug in DJI GO or the OP accidentally chose to set the home point to the current location reported by the mobile device.