Litchi Loss of GPS Question

AirSpace2016 · Feb 2, 2016

Assuming the following scenario with Litchi

Currently flying a mission, loss of signal to video and RC. I know it will continue to fly the mission and most people would either set the mission to RTH, Go back to starting point or have the end way point near the start.

What would happen if you were far enough out when you lost signal to RC and you then lost GPS signal as well. Wouldn't it pop into ATTI mode and then just drift? I know the chances of this is probably quite small and obviously it is illegal to be VLOS but at that point if it was are you screwed until it picked up GPS again?

Mark The Droner · Feb 2, 2016

I would say yes and yes. This kind of scenario is why I like flytrex live 3G

AirSpace2016 · Feb 3, 2016

Has anyone ever experienced this or able to predict what would happen? I messaged people on Litchi facebook who told me it would still return home. Or is this a case of this being too remote to worry about ?

TheRealNick · Feb 3, 2016

AirSpace2016 said:
Has anyone ever experienced this or able to predict what would happen? I messaged people on Litchi facebook who told me it would still return home. Or is this a case of this being too remote to worry about ?

It for sure can not return home without GPS. I think it would auto land after it loses GPS but I don't know for sure...

Mark The Droner · Feb 3, 2016

I've never heard of this happening in the real world. The scenario is very unlikely - very close to impossible. That's because you're not going to be goofy enough to fly a mission with an inadequate number of satellites. You would be sure to have at least an extra satellite or two in case you lose one. But more than likely, as you gained altitude, you'd gain satellites rather then lose them.

Bottom line: Make sure you have plenty of satellites before you launch.

Hope this helps.

Imabiggles · Feb 3, 2016

Marknmd said:
I've never heard of this happening in the real world. The scenario is very unlikely - very close to impossible. That's because you're not going to be goofy enough to fly a mission with an inadequate number of satellites. You would be sure to have at least an extra satellite or two in case you lose one. But more than likely, as you gained altitude, you'd gain satellites rather then lose them.

Bottom line: Make sure you have plenty of satellites before you launch.

Hope this helps.

Be careful, as the recent firmware introduced a bug into any app developed with the SDK that it WILL NOT RTH on loss of RC signal.

Mark The Droner · Feb 3, 2016

I use Litchi with my P2V. The last thing I would expect is an RTH on loss of my RC signal.

ScatSpeak · Feb 3, 2016

AirSpace2016 said:
What would happen if you were far enough out when you lost signal to RC and you then lost GPS signal as well

Seems unlikely that the P3x would lose GPS unless your waypoint mission purposely had it fly into a spot/area where signals would be blocked (inside a tunnel, way up under a bridge, etc.)... which, of course, is somewhat irresponsible and poor planning... Since the mission waypoints are coordinate based, seems unlikely that the P3x could continue the mission if GPS were actually and truly lost... but I don't know what the reaction would be.

Seems you have the opportunity to test it and tell us all about it!

Mark The Droner · Feb 3, 2016

That's a good point. You might have planned it to fly into some tight clearing in a valley or something. Maybe you wanted to take a close look at a small lake. You lose GPS. So what happens next? I would imagine it does the same thing it would do normally. IIRC, it would hover for one minute and then begin to auto-land.

lfaitas · Feb 3, 2016

I fly my p3p pro many times with missions pre-planed using Litchi and send it far far away with eventually total loss of communication but i always make sure the last way point is close to home and that the mission does not last more than 15 mins max to make sure it has enough battery to return back home.
satellite loss will never happen as any mission you dont see the drone will have to be high enough not to hit any trees or buildings so you will get max sat reception of course.
With the auto record on android and curved way points the result is amazing!! i then take screen shots of any pictures i want.
this is one of my videos: because of the tall buildings and me being blocked straight away of any signal for most of the 7 mins flight time i lost total connection of the drone.

Mark The Droner · Feb 3, 2016

This is where Flytrex Live 3G really shines. You lose complete contact with your craft - no FPV no control - but then you bring up your Flytrex app or go to flytrex.com and you can then watch your aircraft as it flies - live on the map.

happydays · Feb 3, 2016

lfaitas said:
I fly my p3p pro many times with missions pre-planed using Litchi and send it far far away with eventually total loss of communication but i always make sure the last way point is close to home and that the mission does not last more than 15 mins max to make sure it has enough battery to return back home.
satellite loss will never happen as any mission you dont see the drone will have to be high enough not to hit any trees or buildings so you will get max sat reception of course.
With the auto record on android and curved way points the result is amazing!! i then take screen shots of any pictures i want.
this is one of my videos:

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because of the tall buildings and me being blocked straight away of any signal for most of the 7 mins flight time i lost total connection of the drone.

There's quite a bit of wobble at 1.00. Was this caused by using Litchi or do you experience this when flying manually as well?

AirSpace2016 · Feb 3, 2016

Another scenario is what happens if it is during a mission and the GPS cuts out (briefly) then regains GPS, will it attempt to go to the waypoint or decide to RTH if it is too much off course?

durrantie · Aug 13, 2016

This is not impossible even in the slightest, it's not at all uncommon for the military to carry out GPS jamming exercises, I have first hand experience of loosing GPS with Litchi and my couple thousand inspire 1 went into P-ATTI mode and just started drifting away from me with no input on the controls

Moby58 · Aug 15, 2016

AirSpace2016 said:
Assuming the following scenario with Litchi

Currently flying a mission, loss of signal to video and RC. I know it will continue to fly the mission and most people would either set the mission to RTH, Go back to starting point or have the end way point near the start.

What would happen if you were far enough out when you lost signal to RC and you then lost GPS signal as well. Wouldn't it pop into ATTI mode and then just drift? I know the chances of this is probably quite small and obviously it is illegal to be VLOS but at that point if it was are you screwed until it picked up GPS again?

If you lose GPS it can never return to home. It wont be able to update where it is, calculate a new heading to home, track that heading, then do it all again. The best that could happen is it knows where it started (home), knows last position when sat lost, then use those 2 coords to calculate heading. There would be no wind correction, etc. This is assuming the compass is still serviceable. Most likely it will proceed on a heading for a certain time (hopeing for sat reacquire), then hover (hopeing for sat reacquire) then autoland.

Jack Bisson · Apr 8, 2018

AirSpace2016 said:
Has anyone ever experienced this or able to predict what would happen? I messaged people on Litchi facebook who told me it would still return home. Or is this a case of this being too remote to worry about ?

I doubt it would return to home without GPS. If it was flying in ATTI mode it could crash if it is out of your line of sight and drifts into a tree or building. When it drifts the chance of the obstacle detection decreases as you could be drifting sideways or backwards. I would always recommend creating a Litchi waypoint mission where you are located in the middle of the mission so you can always see the aircraft and take over the controls if you go into ATTI mode. If things can go wrong they will.

Meta4 · Apr 9, 2018

Jack Bisson said:
I doubt it would return to home without GPS. If it was flying in ATTI mode it could crash if it is out of your line of sight and drifts into a tree or building. When it drifts the chance of the obstacle detection decreases as you could be drifting sideways or backwards. I would always recommend creating a Litchi waypoint mission where you are located in the middle of the mission so you can always see the aircraft and take over the controls if you go into ATTI mode. If things can go wrong they will.

That post you replied to is almost two years old so the original participants probably aren't watching.
But without GPS, the Phantom has no location data.
It can't tell where where it is or how to get to the home point.
But the chances of losing GPS during a mission are close to zero.
You won't lose GPS unless you fly under cover or in a canyon etc or if you mess up the compass, forcing the Phantom into atti mode.

Jack Bisson · Apr 9, 2018

Dude, I am replying because this happened to me today. I lost GPS and my inspire was drifting away that is why I am on this thread. It went into ATTI mode. Not sure what caused the situation, but GPS was lost. Litchi waypoint mission went from NAVI to P_ATTI and did not come back to P_GPS for about 40 seconds. That was a first in many many missions using Litchi. I was in wide open space where I have flown before and this situation came out of nowhere. I should have just flipped the mode switch to sport and then back to p but did not think that quickly enough, I just responded by trying to fly it back to where I was and did. I did not lose radio control at any time during the flight just GPS. It was a little unsettling. Anyway it never happened before and I was looking for others that may have experienced it.

Meta4 · Apr 9, 2018

Jack Bisson said:
Dude, I am replying because this happened to me today. I lost GPS and my inspire was drifting away that is why I am on this thread. It went into ATTI mode. Not sure what caused the situation, but GPS was lost.
I should have just flipped the mode switch to sport and then back to p but did not think that quickly enough, I just responded by trying to fly it back to where I was and did. I did not lose radio control at any time during the flight just GPS. It was a little unsettling. Anyway it never happened before and I was looking for others that may have experienced it.

You might find a clue in the flight data to see what caused the problem.
Go to DJI Flight Log Viewer
Follow the instructions there to upload your flight record from your phone or tablet.
Come back and post a link to the report it gives you.