Fun with M3 GPS - first flight in southern hemisphere

[alex_markov]

I was in the river canyon, as usual, was flying with no GPS but M3 recorded something in the middle of the ocean thousands of kilometers away the only true data is flight length here

 

[EsaT]

At least altitude is positive and not under water...

But better hope that return to home doesn't activate.

 

[alex_markov]

At least altitude is positive and not under water...

But better hope that return to home doesn't activate.

In those cases, I fly nearby to avoid RTH situations as M3 will not return to me for sure

 

[Bussty]

In those cases, I fly nearby to avoid RTH situations as M3 will not return to me for sure

Hi Alex

So what's going on there? How can the drone record a Home Point if it has never had lock? Surely lock can only be activated when the correct HDOP is reached and in that case would be "reasonably" accurate?

Also lets say in your scenario the drone did regain GPS lock and you had a phone malfunction or controller issue and it engaged RTH and sped off towards the middle of the ocean, would there be anything you could do to stop it? Quite scary really I would be wanting DJI to explain how it's creating that Home Point?

When I was testing Dronelink with my Mini a few times it just disengaged and initiated RTH so if I was in your situation I would be in trouble. Mind you I probably wouldn't be testing autonomous drone software in a Canyon

I wonder home many times drone pilots fly drones when the Homepoint isn't right but never engage RTH or have a disconnect to experience a flyaway?

 

[alex_markov]

Hi Alex

So what's going on there? How can the drone record a Home Point if it has never had lock? Surely lock can only be activated when the correct HDOP is reached and in that case would be "reasonably" accurate?

Also lets say in your scenario the drone did regain GPS lock and you had a phone malfunction or controller issue and it engaged RTH and sped off towards the middle of the ocean, would there be anything you could do to stop it? Quite scary really I would be wanting DJI to explain how it's creating that Home Point?

When I was testing Dronelink with my Mini a few times it just disengaged and initiated RTH so if I was in your situation I would be in trouble. Mind you I probably wouldn't be testing autonomous drone software in a Canyon

I wonder home many times drone pilots fly drones when the Homepoint isn't right but never engage RTH or have a disconnect to experience a flyaway?

Dear Bussty, M3 have some GPS issues - they almost solve them with the last update, but in such confined places it just happens sometimes to have no clear coverage - how he record this point is a mystery for me but such things happened - my MP a few years ago changed his home point mid-flight to a position 14 km's away on the other side of the mountain and immediately tried to engage RTH as the battery was obviously not enough to reach it luckily I was able to stop it and return to me on visual ...
My only problem now is DJI prevents M3 to rise more than 30 meters when GPS is poor and I miss some waterfalls and rocks other than that it's OK - there are places where GPS coverage is poor especially when they expect 12+ sats Not inline

 

[Bussty]

Dear Bussty, M3 have some GPS issues - they almost solve them with the last update, but in such confined places it just happens sometimes to have no clear coverage - how he record this point is a mystery for me but such things happened - my MP a few years ago changed his home point mid-flight to a position 14 km's away on the other side of the mountain and immediately tried to engage RTH as the battery was obviously not enough to reach it luckily I was able to stop it and return to me on visual ...
My only problem now is DJI prevents M3 to rise more than 30 meters when GPS is poor and I miss some waterfalls and rocks other than that it's OK - there are places where GPS coverage is poor especially when they expect 12+ sats Not inline

OMG I didn't even think about the battery issue! Of course if you can't get back on remaining battery it will send you home ASAP! So assume you can in that case hit the RTH button to cancel?

What's the forum view? If your drone creates a "false" Home Point then fly's away to get to it.... you SHOULD be covered by DJI for a warranty replacement?

 

[Meta4]

Dear Bussty, M3 have some GPS issues - they almost solve them with the last update, but in such confined places it just happens sometimes to have no clear coverage - how he record this point is a mystery for me but such things happened

It never happened.
Airdata has confused you by putting that H on the map, but the drone never recorded a homepoint.
This is a common glitch with Airdata.
If you looked into the actual flight data, rather than AIrdata's picture, you'd see the lat/long data is blank.
Or post a link to the Airdata report and I can show you.

 

[Meta4]

OMG I didn't even think about the battery issue! Of course if you can't get back on remaining battery it will send you home ASAP! So assume you can in that case hit the RTH button to cancel?

If that's what actually happened (you'd need to look into the data to see if it really did), you would want to reset the drone's home point.

What's the forum view? If your drone creates a "false" Home Point then fly's away to get to it.... you SHOULD be covered by DJI for a warranty replacement?

It's hard to imagine how the drone could create a false home point.
GPS doesn't work like that.

 

[Suren]

Alex, Have you also noticed in Airdata that the flight distance does not show anymore? I have done some long flights recenetly and it shows for me a either 0km or 1km.

 

[Bussty]

If that's what actually happened (you'd need to look into the data to see if it really did), you would want to reset the drone's home point.

It's hard to imagine how the drone could create a false home point.
GPS doesn't work like that.

Ok this is good to know could see massive issues for DJI if was the case. Does ask the question about the 14km issue above, was that just early days with the MP?

 

[Meta4]

Ok this is good to know could see massive issues for DJI if was the case. Does ask the question about the 14km issue above, was that just early days with the MP?

No ... things like that don't happen now and didn't happen in early days of the Mavic Pro.
I'd want to see the flight data to work out what actually happened before accepting that it did.

 

[Bussty]

Confi

No ... things like that don't happen now and didn't happen in early days of the Mavic Pro.
I'd want to see the flight data to work out what actually happened before accepting that it did.

Confidence restored!

 

[Skywatcher2001]

OMG I didn't even think about the battery issue! Of course if you can't get back on remaining battery it will send you home ASAP! So assume you can in that case hit the RTH button to cancel?

Now this is a scary realization . . .

 

[Skywatcher2001]

If that's what actually happened (you'd need to look into the data to see if it really did), you would want to reset the drone's home point.

It's hard to imagine how the drone could create a false home point.
GPS doesn't work like that.

Thank you Meta4 . . . I'm learning a lot.

 

[Bussty]

Now this is a scary realization . . .

Luckily sounds like it should be impossible for drone to create a false homepoint unless your drone and GPS system is having a really bad day in which case DJI should cover you

 

[Skywatcher2001]

Luckily sounds like it should be impossible for drone to create a false homepoint unless your drone and GPS system is having a really bad day in which case DJI should cover you

Yes!! The second I read that, the realization hit me hard. I responded BEFORE I read Meta4''s post that calmed us down and cleared things up. I'm good now . . .

 

[Meta4]

Luckily sounds like it should be impossible for drone to create a false homepoint unless your drone and GPS system is having a really bad day in which case DJI should cover you

Your drone waits until it has good GPS location data before recording a home point.
It doesn't record a home point when it might get a tentative location from a poor quality 2D fix, but waith until it has more satellites in a good geometric array to give a quality 3D fix.

The false alarm that started this thread was due to Airdata mishandling the blank location data and plotting a false "homepoint" on the map display.
Usually Airdata would plot that to 0° S 0° E, which would be north of where it's showing on that map.
The drone never recorded a homepoint at all, because it never had good GPS location data.

 

[Bussty]

Yes!! The second I read that, the realization hit me hard. I responded BEFORE I read Meta4''s post that calmed us down and cleared things up. I'm good now . . .

 

[Bussty]

Your drone waits until it has good GPS location data before recording a home point.
It doesn't record a home point when it might get a tentative location from a poor quality 2D fix, but waith until it has more satellites in a good geometric array to give a quality 3D fix.

The false alarm that started this thread was due to Airdata mishandling the blank location data and plotting a false "homepoint" on the map display.
Usually Airdata would plot that to 0° S 0° E, which would be north of where it's showing on that map.
The drone never recorded a homepoint at all, because it never had good GPS location data.

 

[Bussty]

So to put this all into perspective...

HOMEPOINT ERRORS
Essentially a myth unless you have a faulty drone or decide to make a homepoint at point A then drive to B and not understand why your drone heads back to point A in a RTH or disconnect.

YAW / COMPASS ERRORS
Can absolutely be user error with starting of drone in a magnetic interference area with IMU being set incorrectly to compass then evolving into an impossible YAW correction by IMU once magnetic interference no longer exists.

Can be reduced by...

• Hand launching (without watches etc to interfere with compass of drone) plus should be a long way away from rebar etc
• Making sure drone on DJI Fly app faces same orientation of actual drone

Is that correct?

Any other traps for drone pilots involving location errors/flyways?

Cheers