Losing GPS hold

Valdez · Oct 3, 2019

Two days ago, after taking off, I lost GPS at around 300ft, the drone went into ATTI mode, and started drifting with the wind.

I tried replicating that today. At an indicated 317ft, I have 14/15 satellites, ascend another 20ft, and that number falls to 6/7.

Has anyone else experienced this?

Starz · Oct 3, 2019

Flying in what surroundings?
Middle of no where?
In between buildings?

Valdez · Oct 3, 2019

Starz said:
Flying in what surroundings?
Middle of no where?
In between buildings?

It's nothing obvious like surrounding buildings..

I took off from the top of a fifty metre building, with ten satellites, and no higher buildings in the vicinity. I hovered a while at 50ft, and the satellite count increased to fifteen, then with a stable number of satellites, ascended another 300ft.

The issue occurs at 320ft. Climb any higher, and I seem to lose satellites, half of them in 20ft, and ATTI mode any higher. Descend 20ft, and I regain them fairly instantly. It's almost as if the authorities are disabling GPS above a certain altitude....

Flycaster · Oct 3, 2019

Hmmm, Have you done anything to your setup recently? Updated anything?

Ralph thompson · Oct 3, 2019

I assume your checklist includes "confirm GPS, RC and Telemetry signals" before you takeoff. I check this again at 10', only take 2 secs.

DanMan32 · Oct 3, 2019

He has no issues at low altitudes though.

Filipok · Oct 3, 2019

Considering gps comes from space, I'd have to say there is a magnetic field or transmission causing this.

Meta4 · Oct 3, 2019

Valdez said:
Has anyone else experienced this?

Where is this happening?
That's definitely not normal.
I've seen a couple of similar cases reported.
They were all in Russia

borislip · Nov 1, 2019

I've lost a GPS fix, it went into ATTI and hasn't re-acuire the fix up until i've landed the bird and rebooted it. It has successfully regained the fix after reboot, at the same location. It wasn't in Russia, it was in Atlantic City, NJ, US. It was over a year ago and only happened once. I no longer have the flight logs, but as far as i recall, there was a GPS related error in there, but a very undescriptive one.

dronepilotbob · Nov 1, 2019

I found an area where literally satellites drop from approx 22-24 to about 4-5 and it goes into atti. It’s either very magnetic out there or literally dead area? I’m able to replicate it by going to that particular location. However, I can easily recover by flying away from that area.

Mine has nothing to do with altitude though.

Meta4 · Nov 1, 2019

dronepilotbob said:
I found an area where literally satellites drop from approx 22-24 to about 4-5 and it goes into atti.
It’s either very magnetic out there or literally dead area?

Magnetism won't cause what you describe and there are no dead areas.
It's got to be some sort of interference, but why it doesn't affect all sats sounds unusual.

dronepilotbob said:
I’m able to replicate it by going to that particular location. However, I can easily recover by flying away from that area.

It sounds a little like a report from an urban area in Switzerland where GPS was dropping out when approaching one particular area.
Can you describe the area where this is happening?
What's nearby?

dronepilotbob · Nov 1, 2019

Meta4 said:
Magnetism won't cause what you describe and there are no dead areas.
It's got to be some sort of interference, but why it doesn't affect all sats sounds unusual.

It sounds a little like a report from an urban area in Switzerland where GPS was dropping out when approaching one particular area.
Can you describe the area where this is happening?
What's nearby?

Thanks for your insight.

It’s a creek, and when I get near a bridge (I’m at least 50m in altitude) is when the signal just drops. There is a high school nearby and residential homes. No military, police, ambulance, fire station, or anything that I could think of that’s could interfere with it. Baffled on my end really what sort of interference would make such a significant satellite drop.

I’ll record it next time if it’s of interest along with the area....