One of the things that bugs (scares) me about my Mavic is the complete dependence on the compass.    I'm afraid to do the real things I want - like taking it off from inside my garage or from the back of my truck because I know compass interference could cause issues.    So with that in mind, can someone more experienced or even DJI explain something to me?

Assuming the compass has been calibrated properly at an earlier point/date (ie: no interference), WHEN does the firmware/software take a baseline heading (where it has to be interference free)?   Is it at the time of takeoff, or when updating the GPS RTH point?     For example, does it need to be read before the bird is in the air, or is a new heading registered every time the GPS home point is updated?

I would love to be able to connect, take off from inside my garage (where I know there is compass interference), fly outside over my driveway a ways, then manually update the RTH point (so I have it if I need it), then feel secure that the compass heading was re-read and is ok, regardless of the compass interference that existed inside my garage.   Same with taking off from the bed of a truck...I know there would be interference, so can one just take off, fly a distance out, and reset the homepoint and have the compass heading be re-registered?   

KNOWING when and how the compass is used would help me in making takoff/flight decisions more intelligently.
Thoughts?

Thanks,
LP

I think there is an option to manually set the home point by swiping in on the right of the screen.

Yes. There it is. Of course The compass is unfortunately the main source navigation so the device knows which way its heading.

nottuppaware Posted at 2018-1-21 14:32
I think there is an option to manually set the home point by swiping in on the right of the screen.

Yeah...thanks, but nothing to do with my question.   I knew I could set the home point manually.   My question was about how the compass was related.

LeafPeeper Posted at 2018-1-21 14:50
Yeah...thanks, but nothing to do with my question.   I knew I could set the home point manually.   My question was about how the compass was related.

Sorry I should pay more attention.

We'd need DJI to comment on compass in regards to GPS location. The Mavic has redundant compasses though. Do both of them come up with interference ?

if i understand correctly: the 'baseline' is at take off - actually you should wait until gps/home point is updated before you even launch. where it lifts off from is the home point it will return to. I think flying it down the lane to establish that place as a home point would require flying it there then switching off and switching back on again (but for this you would have to get there to switch it off - in which case you may as well just walk there in the first place and start from there.
However - flying from yr garage does not make sense unless you just want to fly up and down in front of you -  thats at best a few minutes of fun. From within the garage yr LOS is only in front of you to a limited height - if you fly anywhere out side of LOS from inside a garage you will loose signal - so this position you want to fly from is confusing .
From a truck - out in the open even on a truck you should get good gps - in so far as the metal may affect things in theory if you raise it 1.5 m above the surface  (hand launch standing up) or make a falcon post to put the mavic on at the back of yr truck (but make a decent size landing because if the landing is off by a bit and mavic hits the side then it will fall uncontrolabley and likely get damaged)
if you really must fly from yr garage then try to install a retractable roof and fold down walls. -

nottuppaware Posted at 2018-1-21 15:03
Sorry I should pay more attention.

We'd need DJI to comment on compass in regards to GPS location. The Mavic has redundant compasses though. Do both of them come up with interference ?

Nah...both compasses are fine.  The issue is that there are conditions from which I might want to launch where I know there would be ferromagnetic interference.   I was hoping I could just launch, manually fly to a location with less interference, and then manually update the RTH and have the compass behave normally after that.   From the responses I've gotten on the MavicPilots forum, sounds like I'm out of luck.   Launching from a place with high interference is a no-no....

LP

Bekaru Tree Posted at 2018-1-21 15:18
if i understand correctly: the 'baseline' is at take off - actually you should wait until gps/home point is updated before you even launch. where it lifts off from is the home point it will return to. I think flying it down the lane to establish that place as a home point would require flying it there then switching off and switching back on again (but for this you would have to get there to switch it off - in which case you may as well just walk there in the first place and start from there.
However - flying from yr garage does not make sense unless you just want to fly up and down in front of you -  thats at best a few minutes of fun. From within the garage yr LOS is only in front of you to a limited height - if you fly anywhere out side of LOS from inside a garage you will loose signal - so this position you want to fly from is confusing .
From a truck - out in the open even on a truck you should get good gps - in so far as the metal may affect things in theory if you raise it 1.5 m above the surface  (hand launch standing up) or make a falcon post to put the mavic on at the back of yr truck (but make a decent size landing because if the landing is off by a bit and mavic hits the side then it will fall uncontrolabley and likely get damaged)

LOL.   It's more about the weather here.   I have a big garage with a high ceiling....but there are lots of potential sources of interference.  I just wanted to set up my landing pad there, take off, and immediately fly out the garage door.   That way I don't have to trek out into the snow or wet driveway to set up a launch location.   The ONLY reason I'd set the RTH outside the garage is so that if RTH was triggered automatically for some reason it wouldn't try to land on my roof or slam into the garage.

LP

I'm really interested by the upcoming DJI answers here! I got compass issues with my spark and it is really freaking when you feel like loosing control for a few seconds.
Never got one of those with my MPP (yet).
All I know is that DJI recommends to restart the drone if you got interferences before takeoff (can't find a link to this though)

nottuppaware Posted at 2018-1-21 14:35
[view_image]

Yes. There it is. Of course The compass is unfortunately the main source navigation so the device knows which way its heading.

Be careful with these options - they are for the dynamic home point so if you are using a device with a GPS module (cellular) you can reset the home point during flight to where the drone is (HP Aircraft) or to a new location where you are should you move from where you took off during the flight (HP me) if say flying from a moving boat etc. Changing the HP will also deactivate precision landing. If your drone is 500M away and you tap HP aircraft and it loses signal don't expect it to fly back to you... You should always wait for the homepoint to be set on the map before you take off or even arm the motors.

LeafPeeper Posted at 2018-1-21 16:41
Nah...both compasses are fine.  The issue is that there are conditions from which I might want to launch where I know there would be ferromagnetic interference.   I was hoping I could just launch, manually fly to a location with less interference, and then manually update the RTH and have the compass behave normally after that.   From the responses I've gotten on the MavicPilots forum, sounds like I'm out of luck.   Launching from a place with high interference is a no-no....

LP

I would say its a no-no - the homepoint needs to be set at take off then the compass will orientate the northern position in relation to that point for successful return. Taking off in heavy interference will prevent that orientation from the outset.