GPS failed - lesson learned

[Sharky]

Hello everyone!

Wanted to share an experience I had that surprised and scared me at the same time.
The other day I had setup to shoot some video around Baltimore's Inner Harbor. This was going to be my first time flying out over water so I was taking my time getting setup.

I did what I always do, connected the props, syned the phone, etc.
Started up, no errors or warnings of any kind.

Took off and just a few feet away, the GPS failed and it switched to ATTI mode. Also on the screen was a compass calibration fail, which I was surprised I didn't see before it let me launch.

At this point I freaked out. Luckily, I had flown around about a week ago for 10-15 mins in ATTI mode and this helped a lot. Got it under control and brought it back for a landing.

Why everything went bad after launch I am not sure. What saved me was already having flown in ATTI mode and knowing how it reacts.

If you have not flown in ATTI mode yet, find a safe wide open place and do it. It might save your drone from, at least in my case, could have been a slow water death.

The video is on my YouTube page. Feel free to check it out: Chris Roche
You'll see after I landed I attempted a compass recalibration and it kept failing. Shut it down, restarted it up and everything calibrated just fine. The final video came out excellent.

Sharky
DJI Phantom 3 Pro
Part 107 certified

 

[Meta4]

Took off and just a few feet away, the GPS failed and it switched to ATTI mode. Also on the screen was a compass calibration fail, which I was surprised I didn't see before it let me launch.

Did GPS really fail?
It's much more likely to be a compass issue which caused the Phantom to ignore GPS data and drop into atti mode because of conflicting compass and GPS data.
To find out what happened in your case go to https://www.phantomhelp.com/LogViewer/Upload/
Follow the instructions to upload your flight records for the flights in question.
Come back and post a link to the report it provides and someone here might be able to analyse it and give you an understanding of the cause of the incident.

 

[Sharky]

Thanks. File uploaded.
DJI Phantom & Mavic Flight Log Viewer - PhantomHelp.com

Looks like it could have been a compass issue after takeoff that then led to the GPS dropping out.
The yaw errors towards the end were probably me trying to recalibrate after I landed.

 

[Surgeon]

Interesting, the same issue happen to me yesterday but with fatal result. My Mavic just disapperd. Impossible to control, impossible to switch to any other mode. Home didn´t work and the drone just disappeared. Ran after it like a madman but impossible.

 

[Steve7777]

Thanks. File uploaded.
DJI Phantom & Mavic Flight Log Viewer - PhantomHelp.com

Looks like it could have been a compass issue after takeoff that then led to the GPS dropping out.
The yaw errors towards the end were probably me trying to recalibrate after I landed.

I'm no expert but looking at the flight log I would guess that that wharf/pier is just choc-full of reinforcement steel and taking off from it will confuse the compass.. So probably not the best place to launch from, IMHO.

Taking off with the battery at 37% isn't that good either - but that probably wasn't the cause, although some individual cells certainly were a bit iffy for most of the flight.

Glad you got through it anyway.

 

[Sharky]

I'm no expert but looking at the flight log I would guess that that wharf/pier is just choc-full of reinforcement steel and taking off from it will confuse the compass.. So probably not the best place to launch from, IMHO.

Taking off with the battery at 37% isn't that good either - but that probably wasn't the cause, although some individual cells certainly were a bit iffy for most of the flight.

Glad you got through it anyway.

I thought the same thing at first about the wharf, but after I landed, rebooted and relaunched it was fine.

I planned to fly just for a couple minutes on the low battery to check the conditions, set the camera right, etc. Then I put in a fresh one.

 

[Steve7777]

I thought the same thing at first about the wharf, but after I landed, rebooted and relaunched it was fine.

I planned to fly just for a couple minutes on the low battery to check the conditions, set the camera right, etc. Then I put in a fresh one.

Maybe a 'lucky' take-off afterwards, if there is such a thing, but I would certainly avoid any area which is near water and so obviously artificially constructed.

As both you and I know really, it's still not a good idea to take off with a 37% battery, whatever the reason may be... That's not denying that I might have done it in the past though....

 

[Oso]

I'm no expert but looking at the flight log I would guess that that wharf/pier is just choc-full of reinforcement steel and taking off from it will confuse the compass.. So probably not the best place to launch from, IMHO.

I agree. I'm sure that as soon as many of us saw the thread title, before reading the first post we knew it was actually a compass issue and not a GPS issue.
This is almost certainly a flight initiated from a magnetically influenced location. We see it here too often to think anything else.

Taking off with the battery at 37% isn't that good either - but that probably wasn't the cause, although some individual cells certainly were a bit iffy for most of the flight.

I planned to fly just for a couple minutes on the low battery....

We have certainly seen many threads start with a sentence similar to this one, and then end in something unpleasant. I'm also glad it all worked out for you this time.

 

[James McLennon]

I've had the same problem myself flying over a lake but the museum next to me was covered in metal so once I moved away from the building everything was fine. So my question is was there a large amount of metal around your take off? It heavily interacts with your compass and goes into ATTI mode. Just a good job you practiced in ATTI mode, for more practice I advice you get at sh***y small drone, it really helps to hone in your flying skills.

 

[Meta4]

Thanks. File uploaded.
DJI Phantom & Mavic Flight Log Viewer - PhantomHelp.com

Looks like it could have been a compass issue after takeoff that then led to the GPS dropping out.
The yaw errors towards the end were probably me trying to recalibrate after I landed.

You need to look at where you calibrated your compass and/or where you launched.
Your compass error appeared when the Phantom was 6ft above launch point and stayed for the whole flight.
That's a strong indication that either it had a bad calibration (done close to a lot of steel) or you launched from on top of steel (commonly reinforced concrete).
What can you say about where and when you calibrated your compass and the launch point?

 

[Frank Pliska III]

Interesting, the same issue happen to me yesterday but with fatal result. My Mavic just disapperd. Impossible to control, impossible to switch to any other mode. Home didn´t work and the drone just disappeared. Ran after it like a madman but impossible.

Da*mn a Mavic too. Sorry to hear that. This is the kind of comments that scare the hell out of me. Even though I only have a P3S that's still $500 down the drain if it happens to me.

 

[Jesse_M]

Glad you recovered it safely!

Also sorry to the lost Mavic guy...that blows.

 

[James McLennon]

Interesting, the same issue happen to me yesterday but with fatal result. My Mavic just disapperd. Impossible to control, impossible to switch to any other mode. Home didn´t work and the drone just disappeared. Ran after it like a madman but impossible.

Unlucky man did you have it insured or under warranty? Really considering getting mine insured after hearing about all these stories and seeing my old one randomly drop out of the sky.

 

[Sharky]

You need to look at where you calibrated your compass and/or where you launched.
Your compass error appeared when the Phantom was 6ft above launch point and stayed for the whole flight.
That's a strong indication that either it had a bad calibration (done close to a lot of steel) or you launched from on top of steel (commonly reinforced concrete).
What can you say about where and when you calibrated your compass and the launch point?

I don't calibrate before each flight so it was not calibrated here [I've read the "do I or don't I calibrate" arguments, I'm the latter]. The last time was a few weeks prior in a grass field after I accidentally gave it the kill command at 200 feet and it came down into some bushes. Done many flights since then so the crash had no affect on it at all.
[Side note: The worse part of the crash was the battery popping out and the video not saving. I could have made it onto one of those drone crash compilation videos.]

What was under the ground where I launched from I have no clue. It's concrete for sure. The funny thing was, after I rebooted it, I moved about 5 feet away closer to the water, turned it on, no errors at all and it flew fine for 2 entire batteries worth of time.

I'm going to go out on a limb and say it was either just an error during start-up or there was something underground that fowled it up.

Up to this point I never had a GPS or compass error after launch. I've only ever seen it happen right after start-up.

Going to go fly in ATTI mode some more. Good practice!

 

[Meta4]

I don't calibrate before each flight so it was not calibrated here [I've read the "do I or don't I calibrate" arguments, I'm the latter]. The last time was a few weeks prior in a grass field after I accidentally gave it the kill command at 200 feet and it came down into some bushes. Done many flights since then so the crash had no affect on it at all.
[Side note: The worse part of the crash was the battery popping out and the video not saving. I could have made it onto one of those drone crash compilation videos.]

What was under the ground where I launched from I have no clue. It's concrete for sure. The funny thing was, after I rebooted it, I moved about 5 feet away closer to the water, turned it on, no errors at all and it flew fine for 2 entire batteries worth of time.

I'm going to go out on a limb and say it was either just an error during start-up or there was something underground that fowled it up.

Up to this point I never had a GPS or compass error after launch. I've only ever seen it happen right after start-up.

Going to go fly in ATTI mode some more. Good practice!

Most concrete is reinforced and so is half steel. That is almost certainly the cause of the issue.
Never launch from steel or concrete.

 

[dchao]

Agree, launching from concrete ground is like playing russian roulette, because you don't know where the reinforcing steel bars are buried.

 

[martin19117]

Do you normally calibrate the compás every time you fly? I always don't the cumplas calibration procedure every time i fly unless I switch batteries back to back.

Is this recommended?

 

[dchao]

If your drone flew perfectly previously, and you haven't moved location (the earth magnetic field remains constant), there is no need to do another calibration. Because, by doing calibration, there is a small chance of introducing user errors. IMO.

 

[martin19117]

Dchao. I do move location. I normally alway fly in 3 locations but they are far from each other. About 20-30 miles each location. So am I do it correctly by recalibrate the com.

 

[hrosee]

I agree with learning ATTI mode. I have flown RC aircraft since I was a kid. I think a lot a fly aways are caused by people who depend on gps to always be working.