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A GPS Black Hole?

joeke3el

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Jun 25, 2019
Messages
11
Age
59
I was flying manually 10 days ago near my house and suddenly the Spark went into ATTI mode. I began to navigate back manually when it regained GPS and used RTH to bring it home. Over the last 6 days I've been using Litchi quite a bit and noticed the gimbal going crazy in the footage of the general area where I lost GPS in the manual flight. Every time I run the mission the gimbal becomes highly erratic in that spot and finally yesterday the mission stopped one waypoint short and reported that it went into ATTI mode. This phenomenon is all happening in a radius of about 1000 feet. I studied the flight footage and looked over the Litchi logs of yesterday's bad flight and I can only think of perhaps satellite internet interference? It's all residential so I don't know what other transmissions could be taking place. No problem being connected via WiFi in that area as I get a good feed and have complete control. Needless to say, I'm not flying over that way any more and all my Litchi routes are going to be altered to avoid it as well. Was just curious if anyone else has encountered a trouble spot like this. Outside of that radius everything else has been flawless.

Joe
 

jimlips

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Feb 12, 2019
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53
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60
Loc
West Sacramento, CA
Hi joeke3el, welcome to the forum!

When you say, "I lost GPS in the manual flight", do you mean you lost GPS (satellite) lock, or do you mean that you lost contact with the aircraft from your Remote Control (RC)? You did not mention if you were using a RC. Or were you just flying via Wifi on your phone/tablet?

When the aircraft goes into ATTI mode, that typically means that it can't get a GPS lock for whatever reason (view to satellites obstructed, RF interference, etc). But that should not affect the gimbal.

Uploading your flight log here may explain what happened.

If it happened more than once in that area, I would not fly in that area anymore. There may be a high-power TV or Radio station transmitter nearby getting into the gimbal controller itself, but it would likely jam your control telemetry at the same time.

Does it do this with the DJI GO 4 software, or only Litchi?
 

Scooped

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Apr 28, 2019
Messages
21
Age
47
I had same experience with my Spark going into ATTI mode. I was flying near a beach and after a few minutes it went crazy. Able to get it back but almost lost it. I also am not sure why it happened. Was a nice day with marginal cloud cover, no over head trees to block satellites. Hope you get answers as it is a weird experience.
 

jimlips

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Feb 12, 2019
Messages
53
Age
60
Loc
West Sacramento, CA
Before you fly, you might consider checking this website in your area to make sure that there will be enough GPS satellites in view (it also tells you what the winds are likely to be where you will be flying):

UAV Forecast
 
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joeke3el

Member
Join
Jun 25, 2019
Messages
11
Age
59
Hi joeke3el, welcome to the forum!

When you say, "I lost GPS in the manual flight", do you mean you lost GPS (satellite) lock, or do you mean that you lost contact with the aircraft from your Remote Control (RC)? You did not mention if you were using a RC. Or were you just flying via Wifi on your phone/tablet?

When the aircraft goes into ATTI mode, that typically means that it can't get a GPS lock for whatever reason (view to satellites obstructed, RF interference, etc). But that should not affect the gimbal.

Uploading your flight log here may explain what happened.

If it happened more than once in that area, I would not fly in that area anymore. There may be a high-power TV or Radio station transmitter nearby getting into the gimbal controller itself, but it would likely jam your control telemetry at the same time.

Does it do this with the DJI GO 4 software, or only Litchi?
Jim, thanks for your reply. Since posting this I've learned a few more things. ATTI mode happened once while flying manually with the controller and the DJI GO 4 app and also on another day flying autonomously with a Litchi mission. So far I've dived into the Litchi mission issue and have come up with the following:

1. The crazy gimbal activity was due to flight plan gimbal control not executing because the drone was out of RC range. I initially did not know you can't program gimbal movement in areas where there is no RC contact. As a result, when the drone got back into range, all the gimbal commands were pushed through and you can see in the footage all the commands executing in rapid fashion to catch up.
2. I uploaded the Litchi flight log to Airdata.com and looked at the Kp Index at the time of the fight. It was 3-1/3 which is still in the "generally safe" zone but also considered "unsettled" on the chart. I do recall the Spark taking longer than usual to get a lock so in retrospect I probably should have called off the mission. The logs show 15 sats at the moment ATTI kicked in but a Kp of 3-1/3 seems close enough where there may have been a brief moment where it bumped to 5 or 6 and momentarily knocked the drone off. After a few moments of ATTI it did return to GPS which really helped me pilot it home.

Conclusion of the Litchi Mission: My UAV Forecast app only showed 9 sats and even though the Spark had 12 before launch, I should have taken heed to this and waited for better conditions as usually my iPhone app would show at least 12. So things were probably marginal when I launched. I think it all was my fault.

As for the manual flight, I was using the controller, was 143 feet up and about 150 feet from home when it occurred. I have not uploaded that log yet but I was even less experienced on that day and chances are I was flying again when maybe I shouldn't have. The only uncertainty is I was 143 feet above a residential satellite dish when it happened. Not sure if they have internet through that or just TV. Not sure if internet transmission could cause a problem since it's not sharing the same bands as drones. But radio waves have done crazier things to electronics. We'll see. :)


Joe
 

joeke3el

Member
Join
Jun 25, 2019
Messages
11
Age
59
I had same experience with my Spark going into ATTI mode. I was flying near a beach and after a few minutes it went crazy. Able to get it back but almost lost it. I also am not sure why it happened. Was a nice day with marginal cloud cover, no over head trees to block satellites. Hope you get answers as it is a weird experience.
Thanks for the reply, Scooped. One thing I'm adding to my pre-flight check list is checking the geomagnetic disruption (Kp Index) which I found up at Airdata.com. That, and taking my UAV Forecast app more seriously. :)
 

jimlips

Well-Known Member
Join
Feb 12, 2019
Messages
53
Age
60
Loc
West Sacramento, CA
Jim, thanks for your reply. Since posting this I've learned a few more things. ATTI mode happened once while flying manually with the controller and the DJI GO 4 app and also on another day flying autonomously with a Litchi mission. So far I've dived into the Litchi mission issue and have come up with the following:

1. The crazy gimbal activity was due to flight plan gimbal control not executing because the drone was out of RC range. I initially did not know you can't program gimbal movement in areas where there is no RC contact. As a result, when the drone got back into range, all the gimbal commands were pushed through and you can see in the footage all the commands executing in rapid fashion to catch up.
2. I uploaded the Litchi flight log to Airdata.com and looked at the Kp Index at the time of the fight. It was 3-1/3 which is still in the "generally safe" zone but also considered "unsettled" on the chart. I do recall the Spark taking longer than usual to get a lock so in retrospect I probably should have called off the mission. The logs show 15 sats at the moment ATTI kicked in but a Kp of 3-1/3 seems close enough where there may have been a brief moment where it bumped to 5 or 6 and momentarily knocked the drone off. After a few moments of ATTI it did return to GPS which really helped me pilot it home.

Conclusion of the Litchi Mission: My UAV Forecast app only showed 9 sats and even though the Spark had 12 before launch, I should have taken heed to this and waited for better conditions as usually my iPhone app would show at least 12. So things were probably marginal when I launched. I think it all was my fault.

As for the manual flight, I was using the controller, was 143 feet up and about 150 feet from home when it occurred. I have not uploaded that log yet but I was even less experienced on that day and chances are I was flying again when maybe I shouldn't have. The only uncertainty is I was 143 feet above a residential satellite dish when it happened. Not sure if they have internet through that or just TV. Not sure if internet transmission could cause a problem since it's not sharing the same bands as drones. But radio waves have done crazier things to electronics. We'll see. :)


Joe
Joe, I don't know why I did not think of that - while the aircraft will fly fine on a Litchi mission if it loses contact with the RC, the gimbal/camera will no longer aim - you are right, it has to have 100% contact with the RC & phone or tablet to control the pointing of the gimbal. Good catch! I don't know if the Spark is your only aircraft, but I also have a Phantom 3 advanced and a Mavic Pro Platinum. The MPP is by far the best on the Litchi missions. All the camera work is very smooth, where the Spark is a little jerky.

Residential satellite dishes are Receive-Only. That should not affect your drone. Thanks for the update!
 

joeke3el

Member
Join
Jun 25, 2019
Messages
11
Age
59
Residential satellite dishes are Receive-Only. That should not affect your drone. Thanks for the update!
The only other drone I have is the Tello. It's a lot of fun and easy to take out for quick snapshots of places when a larger drone is too much trouble. I'm looking over the Mavic Pro series for an addition to the fleet early next year for larger projects that the Spark may struggle with. Each different sized drone serves a purpose and I think with these three I'd have a tool for every occasion. :)

As for the satellite, I was wondering if my neighbor is using satellite internet, then his uploads would be transmitted. The frequencies they use for that aren't anywhere near WiFi, but anything could happen I suppose. I'll know more when I upload the DJI log for that flight.

BTW, I looked at the history of the Kp Index again at times surrounding that Waypoint flight. It turns out that just around the time my flight was finished the index spiked up to 6! So, maybe that flight was victimized by geomagnetic activity. The lesson for me is to check these things out more thoroughly from now on before launching.

Joe
 

Scooped

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Apr 28, 2019
Messages
21
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47
Well I think I am cursed. Was out flying last night, had roughly 15 satellites and about 1:50 into flight it went absolute crazy mode. I recalibrated imu and GPS before I flew. I could not do anything except watch it crash into tree limbs. I cant remember exactly what it said as my iPad is at home but something like exit GPS imu failure
 

joeke3el

Member
Join
Jun 25, 2019
Messages
11
Age
59
Well I think I am cursed. Was out flying last night, had roughly 15 satellites and about 1:50 into flight it went absolute crazy mode.
Hi Scooped,

Where you near any houses? Just a theory, but I think my Spark got zapped by my neighbor's satellite dish a couple of weeks ago as I suspect they have satellite internet. Unlike TV, the internet package means transmissions come out of those dishes. I don't know them well, but the van that comes by for maintenance is a company that offers satellite internet. I had 16 satellites, was 143 feet up over their house when suddenly "Weak GPS Signal" came up on the screen, I then got the "IMU heading error. Please restart the aircraft." and the Compass Error. Exit P-GPS Mode." errors. It then drifted 500 feet and would not accept an RTH command for a couple of minutes. So, I'm wondering if you were near any houses running internet out of their dishes. I'm still looking into this, but I'm thinking being too close to a transmitting dish is going to be a problem. Not all of these dishes are simply receiving TV so I've been making it a habit to not fly over houses too low since that incident.

I hope your Spark wasn't damaged.

Joe
 

Scooped

Member
Join
Apr 28, 2019
Messages
21
Age
47
Hi Scooped,

Where you near any houses? Just a theory, but I think my Spark got zapped by my neighbor's satellite dish a couple of weeks ago as I suspect they have satellite internet. Unlike TV, the internet package means transmissions come out of those dishes. I don't know them well, but the van that comes by for maintenance is a company that offers satellite internet. I had 16 satellites, was 143 feet up over their house when suddenly "Weak GPS Signal" came up on the screen, I then got the "IMU heading error. Please restart the aircraft." and the Compass Error. Exit P-GPS Mode." errors. It then drifted 500 feet and would not accept an RTH command for a couple of minutes. So, I'm wondering if you were near any houses running internet out of their dishes. I'm still looking into this, but I'm thinking being too close to a transmitting dish is going to be a problem. Not all of these dishes are simply receiving TV so I've been making it a habit to not fly over houses too low since that incident.

I hope your Spark wasn't damaged.

Joe
Nearest house was about 50km away. There was an overpass maybe 400yards away. That's it besides bears, birds and bugs
 

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