"ATTI" Flight Mode -- What Is it; When Is it Forced?

[Rich QR]

GPS uses very short wavelengths, so most receivers use a patch antenna, normally a square about an inch on a side.

You might consider taping some aluminum foil over the top of the drone to attenuate the GPS signal.

Can you determine how many satellites are being received?

Another thought -- I'm not sure if the DJI software will use the phone's location to determine airspace restrictions when the GPS on board the aircraft has no signal. Consider disabling your phone's location services to see if that makes a difference, since a phone can determine location from cell towers (not very precisely) when GPS is unavailable.

 

[Meta4]

It must have a really good GPS receiver onboard. (It's not using my cell phone because I turned off all location services and put it in airplane mode.)

The drone uses its own GPS receiver for all flight purposes.
It does not use GPS data from the phone.

Speculating that the GPS antenna(s) may use the prop arms in addition to the A/C body, I doubt it's possible to shield it(them). Does anyone know anything about this?

The GPS antenna is completely within the body of the drone.

 

[Rich QR]

Launching from reinforced concrete surfaces can cause big problems and the compass is critical for all flight.

The compass is only critical when you have GPS. GPS can't determine orientation by itself, but it can determine direction of movement, for example, to see that the drone is drifting northward. Then the computer knows it needs to head south to correct the drift, and it consults the compass to translate "south" to the proper direction in terms of fore/aft port/starboard.

The vision system measures drift directly in fore/aft port/starboard coordinates, so it doesn't rely on the compass to maintain a stable hover.

 

[Meta4]

The compass is only critical when you have GPS.

It might be better to say: not when the drone is able to use VPS.
It's also critical if you are flying without GPS and VPS.
So it's almost all flight

 

[jclarkw]

GPS uses very short wavelengths, so most receivers use a patch antenna, normally a square about an inch on a side...

19 cm = 7.5" Nevertheless I take your point. I've never seen a GPS antenna larger than a couple of inches. I'll try the foil approach and report... -- jclarkw

 

[DanMan32]

It might be better to say: not when the drone is able to use VPS.
It's also critical if you are flying without GPS and VPS.
So it's almost all flight

Actually no. It's been known for DJI systems to go to ATTI when compass is out of whack, especially years ago with P3. About a year ago my P3 started going weird with FPV tilted. In a few seconds gave a compass error and switched to ATTI where I regained level flight and stable image. As I was orienting myself to get back home, it corrected itself and went back to GPS.

From what I've read over the years with Mavic, particularly since M2, it seems to try to correct for compass error with yaw, often seeming to make the situation worse than dropping to ATTI.

So if you're already in ATTI either by switch or lacking GPS and VPS, then it doesn't use or need compass for FC. However if it's voluntary, then GPS and compass is used for informational telemetry.

 

[DanMan32]

Rebar is a compass problem at a minimum. Guess you were flying ATTI mode... due to lack of satellites.

Sometime GPS, otherwise VPS. Sometimes it did go ATTI if it was too dark.

I was able to get away with it then as geofencing wasn't as strict. The other day I checked out Flysafe map in TIA area to respond in another topic. The garages are in red zones now, so if GPS gets picked up at all, no fly.

I suppose I could go through my flight logs.

 

[jclarkw]

The drone uses its own GPS receiver for all flight purposes.
It does not use GPS data from the phone.

The GPS antenna is completely within the body of the drone.

Meta4 -- What about the communication antenna(s) in the Mavic Air 2? Do you know where it(they) are?

(I wouldn't want to shield them to with any aluminum foil application...) -- jclarkw

 

[MA2 317]

What about the communication antenna(s) in the Mavic Air 2? Do you know where it(they) are?

They are in the front legs.

 

[jclarkw]

MA2 317" data-source="post: 1185722" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch">

They are in the front legs.

MA2 317 -- Thanks! How did you guys get this info? Are there internal diagrams or other technical data available to us? -- jclarkw

 

[slup]

...How did you guys get this info?

You've been a member here since Dec 31:st last year ... look how much you have learned in this short period. Imagine being active in the forum for several years ... your head will be at least twice it's size by then

... and you know, Google & YT is your friends.

 

[jclarkw]

All -- The aluminum foil trick -- see attached photo -- worked reliably to defeat GPS on the lowest level of the house (not so in my attic office, which has three skylights and a large window), so I was finally able to take off, maneuver from room to room, take pictures, and land successfully. (Had to turn off obstacle avoidance to do much.) No issues hovering or maintaining horizontal and vertical position in spite of a concrete slab floor.

Thanks to all the help you folks have provided! -- jclarkw

 

[joenonymus]

I have a new Mavic Air 2, but I'm located inside the Washington, DC, Metro-Area no-drone zone within 15 mi. of Regan National Airport. I want to try out the drone at home before driving to a remote area to play with it. I was hoping to do some test flights inside my house, where the drone probably will not find a GPS location. Before doing so, I was warned on the DJI forum as follows:

"...most often, you will not receive any GPS signal inside the average house, in which case the aircraft will fly in what is called ATTI mode, where it is under full manual flight control. It is a tricky thing to master ATTI mode, and you can very easily fly into walls and other obstacles."

The only thing the user manual says about ATTI mode is the following, which does not suggest the above extreme result:

"The aircraft automatically changes to Attitude (ATTI) mode when the Vision Systems are unavailable or disabled and where the GPS signal is weak or the compass experiences interference [emphasis mine]. In ATTI mode, the aircraft may be more easily affected by its surroundings. Environmental factors such as wind can result in horizontal shifting, which may present hazards, especially when flying in confined spaces."

I'm not an experienced enough pilot to avoid crashing a drone that does not have flight stabilization or collision avoidance -- one of the reasons I bought the Mavic Air 2. I haven't been able to get a straight answer on this from DJI Tech Support. Is it really true that loss of GPS will cause these features to shut down, even if there are sufficient cues for the optical and IR sensors to operate? -- jclarkw

For some real good practice at total manual control buy one of those toy drones like the Hubsan. If you can fly that indoors, you can fly anything. I have one just to practice when the weather won't cooperate and I'm bored. A lot of the little toy drones have no gps.