ATTI to GPS transition while in flight?

[gjhick]

In a scenario such as launching in a cave, and then flying out the entrance into the open air, I’m wondering how the Mavic will behave. Initially it will be in ATTI mode with no home point set. Once it detects satellites, I assume it will auto-switch to GPS? Will it also set a home point, in mid-air?

 

[Simmo]

Good question!! And it might not even be in ATTI, but in OPTI as it never even got sats/gps in the first place??
@msinger ?

 

[gusri.candra]

Are u guys saying three flight mode i.e GPS, OPTI, and ATTI. What the different between ATTI and OPTI.? I thought the same.

 

[Skylane]

Great question. I have hopeful plans of flying through some abandoned train tunnels.

 

[GerdS]

Are u guys saying three flight mode i.e GPS, OPTI, and ATTI. What the different between ATTI and OPTI.? I thought the same.

Atti mode just uses the IMU's accelerometers, gyros and barometric sensor. So the copter behaves similar to a toy copter, just witrh altitude hold. It will slowly drift away in random direction, or even drift fast with wind influence.
Compared to that, Opti mode is using the downward looking cameras, the VPS system in addition to support the IMU with drift information derived out of the video stream, so the IMU can compensate, similar as it does if GPS is available. Therefore in Opti mode the copter will stay at place without drifting.

If taking off in Atti or Opti mode the Mavic will set its homepoint as soon as it will get a valid GPS position.

 

[MacPap]

Yes it will set home point in mid air. Same AS IF YOU started it and flew away before it has set home point. All that of course provided one uses a firmware that does not require sal lock prior to flying.

 

[Simmo]

Yes it will set home point in mid air. Same AS IF YOU started it and flew away before it has set home point. All that of course provided one uses a firmware that does not require sal lock prior to flying.

Please point to some documentation that says this? (setting the home point in mid air)

 

[sar104]

Please point to some documentation that says this? (setting the home point in mid air)

I don't think that is explicitly stated in the manual but it is stated that the home point is recorded when sufficient satellite signals are locked to provide a location (Page 13):

"If a strong GPS signal was acquired before takeoff, the Home Point is the location from which the aircraft launched. The GPS signal strengthis indicated by the GPS icon ( ). The aircraft status indicator willblink rapidly when the home point is recorded."
​

The case in question is a corollary to that since it is, by default, in ATTI or OPTI mode before it acquires a position, and since there is no time limitation on how long it takes to acquire position. That aside - that behavior has been common knowledge for years and is apparent in flight logs - it is certainly correct.

 

[Simmo]

Thankyou @sar104 and you too @MacPap
I add more knowledge today, thats a good day. Thankyou!

 

[sonof40]

Until you get all the info, you could try launching outside the cave, then flying in and start recording.

 

[gusri.candra]

Has someone tested it..? My thought, it is quite safe as the home point is set when it takes off. when the satellite reception lost or recover during mid flight will have no impact on the preset home point. It's worth to test.

 

[gjhick]

Has someone tested it..? My thought, it is quite safe as the home point is set when it takes off. when the satellite reception lost or recover during mid flight will have no impact on the preset home point. It's worth to test.

I was asking about a situation where there is no satellite availability at the take-off point ....and consequently no possibility of the home-point being set until the Mavic has flown off to a different area that does allow for satellite signals.

 

[gusri.candra]

I was asking about a situation where there is no satellite availability at the take-off point ....and consequently no possibility of the home-point being set until the Mavic has flown off to a different area that does allow for satellite signals.

It may use previous home point

 

[dbyantis]

I was asking about a situation where there is no satellite availability at the take-off point ....and consequently no possibility of the home-point being set until the Mavic has flown off to a different area that does allow for satellite signals.

I have read flight logs posted on this forum that show a Home Point(HP) getting set well after launch in mid-air, I always wondered what would happen on return. I assumed hover until critical battery landed.

 

[HWCM]

It may use previous home point

No it will not.

 

[HWCM]

I have read flight logs posted on this forum that show a Home Point(HP) getting set well after launch in mid-air, I always wondered what would happen on return. I assumed hover until critical battery landed.

It will return to the recorded home point and land. It records home point location, not altitude.

 

[sar104]

I have read flight logs posted on this forum that show a Home Point(HP) getting set well after launch in mid-air, I always wondered what would happen on return. I assumed hover until critical battery landed.

The home point does not constrain altitude. It will continue to descend until it lands.

 

[Aussie Mick]

Yes it will set home point in mid air. Same AS IF YOU started it and flew away before it has set home point. All that of course provided one uses a firmware that does not require sal lock prior to flying.

may i ask what is sal lock ?

 

[Simmo]

SaT lock..

 

[Greg B 37066]

I had this happen when starting out between large buildings. When I hit RTH by accident it went up between the buildings where it originally acquired. Had to override to land.