Hello,

I keep getting the same issue with losing GPS signal at an altitude between 30 and 80m at a temperature between 1°C and 3°C when there are higher winds (the battery was at room temparature each time when I started the flight).
It always happened at the same location in a park above a small lake. https://www.google.com/maps/place/Schwanenteich,+18069+Rostock/@54.0969199,12.0870127,19z/data=!4m2!3m1!1s0x47ac57292762281b:0xd7e59f3647b7efd8
There are no metal structures nearby.

The signal is back after 10-60 seconds. One time I could only prevent a fly-away by going into sports mode and manually stopping the copter from drifting away.

The copter was less than 100m away from my position.

Any clues?

Maybe upload the flight log to http://www.phantomhelp.com/LogViewer/upload/ so that we can see what happened...

You might consider the possibility of GPS signals bouncing off the smooth surface of the lake causing you to lose an accurate fix.  

I would also recommend not flying if the wind is so high you need sport mode to stop it drifting away!

How many satellites did you have when you started?

ALABAMA Posted at 2018-2-21 11:40
How many satellites did you have when you started?

About 12 satellites.

Simple fix .... dont fly in that location again
There is obviously a gps dead spot over the lake for whatever reason so i would classify that as a no fly zone if i were you.

Hellsgate Posted at 2018-2-21 12:20
Simple fix .... dont fly in that location again
There is obviously a gps dead spot over the lake for whatever reason so i would classify that as a no fly zone if i were you.

Correct, at least until you find something else.

Mark The Droner Posted at 2018-2-21 11:30
You might consider the possibility of GPS signals bouncing off the smooth surface of the lake causing you to lose an accurate fix.

If the wind was blowing hard enough to cause the drone to drift away fast then i doubt the surface of the lake would have been smooth enough to reflect gps signals there must be another reason for it

http://www.phantomhelp.com/LogViewer/W2PQSVXCRDJGRKH3CA6U/
This was the last time this had happened. At that occasion I started with only 8-10 satellite fixes.

It is the cold air. The signal is coming back once the heat from the battery warms up the electronics.

MartinRJ Posted at 2018-2-21 12:01
About 12 satellites.

12 satellites is very low, especially with a very flat landscape, no big hills, maybe you should have waited for it to find some more before taking off?

Or is 12 normal for your aircraft?  If so then maybe there is a fault with your GPS receiver...

Are there any microwave transmitters in the area?
These transmiters can have very powerful signals that can easily block out a gps signal similar to a signal jammer used by the army they normally happen above ground level and when in a direct line between the two towers.
These signals normaly wont be apparent at ground level because the signal between the 2 towers is highly directional but if your drone flies into the path of one of these microwave signals it is possible that the gps signal may get jammed by it.
Anyway just a posibilty

Nigel_ Posted at 2018-2-21 12:38
12 satellites is very low, especially with a very flat landscape, no big hills, maybe you should have waited for it to find some more before taking off?

Or is 12 normal for your aircraft?  If so then maybe there is a fault with your GPS receiver...

Here it takes several minutes (3-5) until I get 15 satellite fixes.
Usually I start with 10+.
I'm still new to quadcopters though, this is my first drone. And I've only had it for 2 weeks.

MartinRJ Posted at 2018-2-21 12:41
Here it takes several minutes (3-5) until I get 15 satellite fixes.
Usually I start with 10+.
I'm still new to quadcopters though, this is my first drone. And I've only had it for 2 weeks.

I think most people would get around 20 in a location like that.  

I suggest you try it away from the city and other sources of interference, if it still takes 5 minutes to get only 15 then I think the receiver has a fault.  If it is only a problem at that location, maybe fly somewhere safer.

The signal reflecting off the water is my vote.  Is there anything just under the water (fountain piping?)

VigilanteDrones Posted at 2018-2-21 13:26
The signal reflecting off the water is my vote.  Is there anything just under the water (fountain piping?)

Yes exactly that

This was the first time this happened: http://www.phantomhelp.com/LogViewer/H6L7E0USCIFWCPEJYF2B/
It started with "Magnetic Filed Interference. Exit P-GPS Mode; Yaw Error"
and then it said
"Flight Mode Set to Attitude__Set the Flight Mode to P-mode to ensure flight safety.; Yaw Error"
and eventually "Cannot start Return to Home due to weak GPS signal. ; Yaw Error"

although the copter had 17satellite fixes.

MartinRJ Posted at 2018-2-21 13:55
This was the first time this happened: http://www.phantomhelp.com/LogViewer/H6L7E0USCIFWCPEJYF2B/
It started with "Magnetic Filed Interference. Exit P-GPS Mode; Yaw Error"
and then it said

The problem there is that you took off too close to some metal, maybe a car, underground pipes/cables, a cast iron grid?

Once you got to 15m height you left the magnetic field of the metal and the roll and yaw become inaccurate and the aircraft is unsteady, it dropped into atti mode for a while because the compass data didn't match the gps data.

MartinRJ Posted at 2018-2-21 13:55
This was the first time this happened: http://www.phantomhelp.com/LogViewer/H6L7E0USCIFWCPEJYF2B/
It started with "Magnetic Filed Interference. Exit P-GPS Mode; Yaw Error"
and then it said

Looking at the flight log, your issue had nothing at all to do with GPS reception, in fact it was receiving at 16 satellites for much of the flight. The yaw error is related to compass issues, and suggests the compass was influenced by some metal object at launch.
I see Nigel has beaten me to it.

Nigel_ Posted at 2018-2-21 14:31
The problem there is that you took off too close to some metal, maybe a car, underground pipes/cables, a cast iron grid?

Once you got to 15m height you left the magnetic field of the metal and the roll and yaw become inaccurate and the aircraft is unsteady, it dropped into atti mode for a while because the compass data didn't match the gps data.

There was a metal fence about 10m away from the starting position. Could it be that?

MartinRJ Posted at 2018-2-21 14:42
There was a metal fence about 10m away from the starting position. Could it be that?

No, too far away. It had to be something closer. Perhaps buried water pipes?

Geebax Posted at 2018-2-21 14:43
No, too far away. It had to be something closer. Perhaps buried water pipes?

Apart from that there were only trees, really.

MartinRJ Posted at 2018-2-21 14:45
Apart from that there were only trees, really.

Reinforced concrete?

Labroides Posted at 2018-2-21 15:23
Reinforced concrete?

No, it's only a meadow in a park, between some trees.
I just went there again to measure the magnetic field, and there are zero abnormalities at the entire meadow.
I even checked the gear that I was carrying (e.g. a mobile router) but the magnetometer also doesn't detect any deviation there.

Thinking about it again, you may be right. I think at that particular flight I started right next to said metal fence, because there are some pavers next to it, and I had forgotten to bring my landing pad with me!

MartinRJ Posted at 2018-2-21 15:36
Thinking about it again, you may be right. I think at that particular flight I started right next to said metal fence, because there are some pavers next to it, and I had forgotten to bring my landing pad with me!

Whatever it was had an influence on the compass up to 15m height, so it was either tall or very substantial.
I would go with the fence.

MartinRJ Posted at 2018-2-21 15:36
Thinking about it again, you may be right. I think at that particular flight I started right next to said metal fence, because there are some pavers next to it, and I had forgotten to bring my landing pad with me!

'because there are some pavers next to it, and I had forgotten to bring my landing pad with me!'

There is your answer right away. Large pavers are often reinforced with steel mesh.

MartinRJ Posted at 2018-2-21 13:55
This was the first time this happened: http://www.phantomhelp.com/LogViewer/H6L7E0USCIFWCPEJYF2B/
It started with "Magnetic Filed Interference. Exit P-GPS Mode; Yaw Error"
and then it said

Hi.

Have seen something similar to the same error on my P4A that is almost identical to yours. After calibrating the compass, the errors disappeared.

Another thing is that in the cities there are often buried high-voltage cables in the underground. You can often not see what is on the spot. For the same reason, I suggest you find somewhere outside the city to fly. You also get error messages on the new spot you should take your P4P at the dealer you bought it to a Guarantee repair.

Regards Leif.

Martin, is there any chance change to another open location without interference? It will be helpful to narrow down the scope and locate the exact status. Please help us confirm, thanks!

DJI Susan Posted at 2018-2-22 01:18
Martin, is there any chance change to another open location without interference? It will be helpful to narrow down the scope and locate the exact status. Please help us confirm, thanks!

I have been using the drone at several locations.
And the only occasions when the signal was lost (either compass or GPS) was around that lake.

I will continue keeping a close eye on this, and will update this thread when it happens again.

MartinRJ Posted at 2018-2-22 01:27
I have been using the drone at several locations.
And the only occasions when the signal was lost (either compass or GPS) was around that lake.

Noted with thanks! Please keep us posted on the latest progress.