Weird problem: Telemetry distance constantly fluctuates

[langcpht]

How much of the sky is visible from your outdoor observation spot?

A very large amount. Very occasionally I will fly in a dense area that has very little visible sky, (around a forested waterfall for example) but the vast majority of the time I'm in an area open enough to see at least 75% of the sky straight above without any obstructions.

 

[Meta4]

A very large amount. Very occasionally I will fly in a dense area that has very little visible sky, (around a forested waterfall for example) but the vast majority of the time I'm in an area open enough to see at least 75% of the sky straight above without any obstructions.

Thanks .. flight data is needed to go any further.

 

[langcpht]

The telemetry is what the app is displaying and recording, so it should be reflected in the log.

I've attached a TXT flight record. I poked around for the mobile DAT file but I have no folder or files for it. I guess this is a common problem for Android users.

 

[langcpht]

Thanks .. flight data is needed to go any further.

The post above has my most recent TXT flight record. I cannot say whether the problem was exhibited during this flight or not as I wasn't actively checking the telemetry data for that particular flight.

 

[sar104]

I've attached a TXT flight record. I poked around for the mobile DAT file but I have no folder or files for it. I guess this is a common problem for Android users.

You never went more than around 20 m from the home point in that flight, so it's not a great sample. The telemetry data look reasonable though:

 

[Meta4]

I've attached a TXT flight record. I poked around for the mobile DAT file but I have no folder or files for it. I guess this is a common problem for Android users.

That flight data looks like this:DJI Flight Log Viewer - PhantomHelp.com

This flight is not ideal for checking GPS stability because most of the flight is down low in a forested area.
The GPS Health was rated at 4/5 until 11:56.5 when the drone was 39 ft above the level of the launch point.
I looked at data from a section of the flight where the GPS Health was was 5/5 and the drone was in stable hover.

This was for 13.5 seconds (136 data records) of the flight from 11:59.1.
Here is a screenshot of some of that data:

You can see that the GPS location data (blue & yellow) is varying with each 1/10th of a second.
It's quite normal for GPS to do this and variation of 1-2 metres happens all the time.
It's the amount of this variation that matters.

In the 72 records I used as a sample the longitude variation was quite small.
The variation in latitude was 0.00000131 of one degree.

Since one metre = 0.00001 degree of latitude (approximately), the amount of variation exhibited is trivial.

At least for this small section of this flight, the GPS location data is reliable and not wandering to any significant degree.

To check further, the ideal flight data would be from a "flight" where teh drone is just sitting (not flying) for 5 minutes or so.

 

[langcpht]

Thanks to both of you guys for checking this out for me. I'm sorry if it wasn't a great example, but I never fly very far or very high. All my flights are like that, short, low-altitude, and close to takeoff.
If you guys seem to think things are within tolerance I'll just shut up and fly. It just seems weird, ya know?

 

[Meta4]

Thanks to both of you guys for checking this out for me. I'm sorry if it wasn't a great example, but I never fly very far or very high. All my flights are like that, short, low-altitude, and close to takeoff.
If you guys seem to think things are within tolerance I'll just shut up and fly. It just seems weird, ya know?

I'd really need to see more to be able to say anything.
Perhaps there's a real issue that wasn't showing up in that flight.
The numbers you mentioned in your OP are quite different from what was happening in that flight.
It would be interesting to see the data if the distance is wandering as you described.

 

[boblui]

I cannot see any anomalities in the postion of the craft but the position of the phone jumped around over an area that spans about 1 km ! Either you are Flash the super hero or there is some problem with the phone's GPS.

The blue track is for your phone, the red track is for the craft :





This explains why the distance from the contoller displayed on the GO app fluctuated wildly. However, it does not explain the fluctuation in the distance from the home point. May be there is a software bug in the GO app in this regard.

 

[langcpht]

I cannot see any anomalities in the postion of the craft but the position of the phone jumped over an area that spans about 1 km !

The blue track is for your phone, the red track is for the craft :

View attachment 106639

View attachment 106640

This explains why the distance from the contoller displayed on the GO app fluctuated wildly. However, it does not explain the fluctuation in the distance from the home point. May be there is a software bug in the GO app in this regard.

This stuff more closely aligns with what I'm experiencing. Perhaps this is entirely related to my phone and not with the aircraft?
Again, I REALLY appreciate you guys taking time to check this out.

 

[boblui]

This stuff more closely aligns with what I'm experiencing. Perhaps this is entirely related to my phone and not with the aircraft?

It's very unlikely that the craft has got problems. The phone may be OK as well but the GO app may be getting incorrect GPS data from the phone for some reasons.

 

[langcpht]

It's very unlikely that the craft has got problems. The phone may be OK as well but the GO app may be getting incorrect GPS data from the phone for some reasons.

I'm considering buying a Smart Controller, anyway. My phone just isn't bright enough in direct sunlight to see much of anything. My only concern now is activating Return to Home; I'm guessing that as long as I don't use the position of my phone as return destination and strictly use the takeoff point as return destination I'll probably be just fine.

 

[Meta4]

I'm considering buying a Smart Controller, anyway. My phone just isn't bright enough in direct sunlight to see much of anything. My only concern now is activating Return to Home; I'm guessing that as long as I don't use the position of my phone as return destination and strictly use the takeoff point as return destination I'll probably be just fine.

The phone's location data doesn't matter for anything in general flying.
And the phone's GPS might be OK anyway.
I'd want to investigate the phone data further before deciding that it's not working properly.

 

[sar104]

The phone location data are certainly bad - that's not normal:





No problems with the aircraft data though.

 

[Meta4]

The phone location data are certainly bad - that's not normal:

That's very strange.
It's not wandering a few metres as GPS does.
It's repeatedly jumping 500-800 metres.

 

[sar104]

That's very strange.
It's not wandering a few metres as GPS does.
It's repeatedly jumping 500-800 metres.

You sometimes see that with devices that continue to report location even when the position solution is very poor. With phones it can be due to them falling back on A-GPS data, such as cell towers and wifi network signals.

 

[langcpht]

You sometimes see that with devices that continue to report location even when the position solution is very poor. With phones it can be due to them falling back on A-GPS data, such as cell towers and wifi network signals.

Again, I really appreciate you guys digging into this for me. It sounds as though the problem is superficial and unlikely to impact the performance or reliability of my aircraft. Is it worth going deeper with this?

 

[sar104]

Again, I really appreciate you guys digging into this for me. It sounds as though the problem is superficial and unlikely to impact the performance or reliability of my aircraft. Is it worth going deeper with this?

In that location it is quite likely just a lack of satellites available to the phone. It's not going to affect flight performance.