GPS signal losing

Ivanoleksii1997 · Dec 28, 2017

Hello everyone! I'm flying with my Phantom 4 advanced and enjoy it very much. However last couple flights were not successful and I almost lost/crashed my drone.
Because of GPS signal that was losing after around 15 seconds of flight, the the Phantom 4 was switched into ATTI mode and no positioning was screened. As a result it headed disorderly into a random direction, after I literally had to catch because the drone didn't hover but was just flying into some direction.

Please note: the satellite level was at about 10 points and GPS signal was just fine while at the ground and during first 10 - 15 seconds. Then all this situation had occurred. Has anyone ever faced with something like this? Or any clue about how to fix this?

Thank you!

sar104 · Dec 28, 2017

The cause is likely nothing to do with poor GPS reception. The aircraft will switch to ATTI mode if its magnetometer (compass) data disagree with the IMU-computed heading. That could be due to taking off from a location with magnetic distortion (concrete with rebar for example) or it could be that the compass needs to be calibrated, especially likely if you have added an additional components recently.

Ivanoleksii1997 · Dec 28, 2017

sar104 said:
The cause is likely nothing to do with poor GPS reception. The aircraft will switch to ATTI mode if its magnetometer (compass) data disagree with the IMU-computed heading. That could be due to taking off from a location with magnetic distortion (concrete with rebar for example) or it could be that the compass needs to be calibrated, especially likely if you have added an additional components recently.

Thank you! But the thing is that priorly it worked just fine in the same location, whereas, now it happens like I described before. Is there any other reason for this?

I also had an experience testing different objects installed under the drone and due to this it could fly normally with them, so I landed it right away. Could I damage something in this way?

Meta4 · Dec 28, 2017

Ivanoleksii1997 said:
Thank you! But the thing is that priorly it worked just fine in the same location, whereas, now it happens like I described before. Is there any other reason for this?

The way to find out is to look at the flight data.
Go to: DJI Flight Log Viewer
Follow the instructions, come back and post a link.

Ivanoleksii1997 said:
I also had an experience testing different objects installed under the drone and due to this it could fly normally with them, so I landed it right away. Could I damage something in this way?

The compass is in the landing gear.
Putting steel or electrical items close to the compass can make it malfunction which will make your Phantom ignore GPS data and go into atti mode.
In atti mode with a compass malfunction, your Phantom will be unpredictable and hard to control.

Ivanoleksii1997 · Dec 28, 2017

Meta4 said:
The way to find out is to look at the flight data.
Go to: DJI Flight Log Viewer
Follow the instructions, come back and post a link.

The compass is in the landing gear.
Putting steel or electrical items close to the compass can make it malfunction which will make your Phantom ignore GPS data and go into atti mode.
In atti mode with a compass malfunction, your Phantom will be unpredictable and hard to control.

Hello! Thank you for your message here is the link DJI Flight Log Viewer - PhantomHelp.com

Meta4 · Dec 28, 2017

Ivanoleksii1997 said:
Hello! Thank you for your message here is the link DJI Flight Log Viewer - PhantomHelp.com

For that flight, GPS was lost rather than compass issues just causing the Phantom to ignore GPS data.
Does the Phantom get sats now if you start it up outdoors?
Or has it lost GPS permanently?
The cause may be a broken GPS antenna (have you crashed?) or a bad connection between the GPS receiver and the mainboard.

ps ... I see that you started the flight with the battery level at 52%.
Launching with a partially discharged battery is a good way to lose the Phantom, particularly in cold conditions.
Always fly with a fully charged battery.

Ivanoleksii1997 · Dec 28, 2017

Meta4 said:
For that flight, GPS was lost rather than compass issues just causing the Phantom to ignore GPS data.
Does the Phantom get sats now if you start it up outdoors?
Or has it lost GPS permanently?
The cause may be a broken GPS antenna (have you crashed?) or a bad connection between the GPS receiver and the mainboard.

ps ... I see that you started the flight with the battery level at 52%.
Launching with a partially discharged battery is a good way to lose the Phantom, particularly in cold conditions.
Always fly with a fully charged battery.

Okay! I see you about the battery. But other than this
1) It happened before that GPS was lost, however at some flights it functioned just fine
2) Where is GPS antenna located? - It has never been crashed badly, however it didn't land properly couple of times (not horizontally but a little bit bent due to not hovering but flying to sides, if you know what I mean) Besides this, it has never been crashed.
3) After restarting it, Phantom works the same way (so first 10 - 15 seconds with GPS, then losing the signal)
4) DJI Flight Log Viewer - PhantomHelp.com this is the data of the flight before any type of even small crashes, just when I started using it.

What do you think it could be the issue

Meta4 · Dec 28, 2017

Ivanoleksii1997 said:
What do you think it could be the issue

That's very unusual, normally GPS is trouble free.
The GPS antenna is under the top of the shell.
I think I have seen a post about GPS jamming problems in Moscow that caused unusual loss of GPS signal - but you are a long way from there.
And the other flight you posted is at a very different location so jamming might not be involved?

Ivanoleksii1997 · Dec 28, 2017

Meta4 said:
That's very unusual, normally GPS is trouble free.
The GPS antenna is under the top of the shell.
I think I have seen a post about GPS jamming problems in Moscow that caused unusual loss of GPS signal - but you are a long way from there.
And the other flight you posted is at a very different location so jamming might not be involved?

Yeah! that's true, very far away. But still, you seem to be professional, what would you suggest to do?

Ivanoleksii1997 · Dec 28, 2017

Ivanoleksii1997 said:
Yeah! that's true, very far away. But still, you seem to be professional, what would you suggest to do?

And you think it has nothing to do with calibration or satellite weak signal or something like this?

Meta4 · Dec 28, 2017

Ivanoleksii1997 said:
And you think it has nothing to do with calibration or satellite weak signal or something like this?

Definitely not.
There's nothing you can calibrate or adjust for GPS.
GPS signal is always strong - there's nothing between the GPS satellite and your receiver.

Ivanoleksii1997 · Dec 28, 2017

If

Meta4 said:
Definitely not.
There's nothing you can calibrate or adjust for GPS.
GPS signal is always strong - there's nothing between the GPS satellite and your receiver.

If not, what it could be?

Meta4 · Dec 28, 2017

Ivanoleksii1997 said:
If not, what it could be?

It's unusual.
Do you know of any other Phantom owners flying there?

Ivanoleksii1997 · Dec 28, 2017

Just one of them, and everything works properly...
Do you think DJI could repair it?

Meta4 · Dec 28, 2017

Ivanoleksii1997 said:
Just one of them, and everything works properly...
Do you think DJI could repair it?

If others can fly in the same area with normal GPS, that suggests there's a problem with yours.
Perhaps a poor connection that disconnects with vibration?
If yours has been like this from new, I'd be looking for a warranty repair/replacement from DJI.

sar104 · Dec 28, 2017

Meta4 said:
If others can fly in the same area with normal GPS, that suggests there's a problem with yours.
Perhaps a poor connection that disconnects with vibration?
If yours has been like this from new, I'd be looking for a warranty repair/replacement from DJI.

I agree. Both the flights posted showed apparently random transitions from numerous satellites to zero. I'd, check the antenna and its connection first, but failing those showing any problems it's going to be the GPS module or its connection to the FC.