Drone flew 600m away from me - out of my control!

[Deleted member 94047]

If you are interested in the fix - it really is simple. This is the function code, where data_wave is passed as the field to be fixed. Note that offsetmax is determined by inspection.

Function fix(data_wave)​

Wave data_wave​

int n​

variable offsetmax​

WaveStats data_wave​

offsetmax = 20 ​

n = 1​

do​

if (abs(data_wave[n] - data_wave[n-1]) > offsetmax)​

data_wave[n] = data_wave[n-1]​

endif​

n+=1​

While (n < V_npnts)​

End​

OK, that is alien to me but I thank you nonetheless. Hopefully, someone else will find it helpful.

 

[slup]

OK, that is alien to me but I thank you nonetheless. Hopefully, someone else will find it helpful.

Yeah @Doppler ... we have still far to crawl until we can walk as @sar104

 

[MAvic_South_Oz]

Extrapolating velocity to that time gives the following as a track:

@SamCrouch that gives some hope . . . it seems more than likely it would have 99.9% made landfall, a much better option than the loch bed.
It is a long shot, but if you're in a position to go back and try a search radiating out from that yellow pin, well, you might get lucky.
I guess the weather now is the issue !!

 

[Prismatic]

If you are interested in the fix - it really is simple. This is the function code, where data_wave is passed as the field to be fixed. Note that offsetmax is determined by inspection.

Function fix(data_wave)​

Wave data_wave​

int n​

variable offsetmax​

WaveStats data_wave​

offsetmax = 20 ​

n = 1​

do​

if (abs(data_wave[n] - data_wave[n-1]) > offsetmax)​

data_wave[n] = data_wave[n-1]​

endif​

n+=1​

While (n < V_npnts)​

End​

So the corruption amounts to a "shift +1” in an array (a.k.a. vector) of data points. The fix is to perform a “shift -1” on the array. Yeah?

Questions:

1. Why do we test the absolute value of a data point against the actual value of its predecessor? Seems odd.
2. What does the empirical offsetmax really mean? It suggests there’s a discontinuity in the (corrupted) data, but I’m not sure.
3. Probably related to other logic, but why declare Wave and WaveStats? They’re not used here.
4. Minor point: I assume V_npts is defined globally, probably the common array length of all fields.

 

[BudWalker]

If you are interested in the fix - it really is simple. This is the function code, where data_wave is passed as the field to be fixed. Note that offsetmax is determined by inspection.

Function fix(data_wave)​

Wave data_wave​

int n​

variable offsetmax​

WaveStats data_wave​

offsetmax = 20 ​

n = 1​

do​

if (abs(data_wave[n] - data_wave[n-1]) > offsetmax)​

data_wave[n] = data_wave[n-1]​

endif​

n+=1​

While (n < V_npnts)​

End​

I started attempting to fix the .csv in Excel but gave up after 5 minutes when I could see that it would take the better part of an hour. My approach was similar. Instead of replicating the previous row I was deleting the bad rows.

 

[sar104]

@sar104 - That's great work.

Can you explain (in pretty simple terms!) how on earth you corrected those data files? So the numbers and errors could not of just been random?

There must of been of been a pattern? How did you spot it and quantify it?

The corruption was in the form of random brief offsets from the real data in all the fields, including the flight time. Starting with that, if you look at the OSD_flyTime data as a function of point number, you will see the following:



The time data should increment by 0.1 seconds each point, but in some cases there are large data offsets. So that's easily fixed by detecting the discontinuous outliers and replacing them with the appropriate time step, being careful not to overwrite the small real discontinuities at the end that reflect data loss. That gives:



Now that the time data are fixed, the same basic algorithm can be applied to other data which have similar problems, such as height:





That method is then applied to each data field.

 

[sar104]

I started attempting to fix the .csv in Excel but gave up after 5 minutes when I could see that it would take the better part of an hour. My approach was similar. Instead of replicating the previous row I was deleting the bad rows.

Yes - with nearly 10,000 rows to go through that's going to be very time consuming. You could write a similar conditional script in Excel, but Igor is much easier.

 

[sar104]

So the corruption amounts to a "shift +1” in an array (a.k.a. vector) of data points. The fix is to perform a “shift -1” on the array. Yeah?

Questions:

Why do we test the absolute value of a data point against the actual value of its predecessor? Seems odd.

Because we have to decide if the change in data is real or spurious. The only dependable method is to note that the spurious changes are too large to be physical, and so the test is to compare with the previous data point. The abs function just allows a single test to detect positive or negative excursions.

What does the empirical offsetmax really mean? It suggests there’s a discontinuity in the (corrupted) data, but I’m not sure.

It's the threshold set to determine if the change was too large.

Probably related to other logic, but why declare Wave and WaveStats? They’re not used here.

Yes they are. The wave declaration is required to declare that data_wave is a wave. The WaveStats function generates, amongst other things, the standard variable V_npnts which is used to close the do loop.

Minor point: I assume V_npts is defined globally, probably the common array length of all fields.

No - it's an output result for the wave that WaveStats operated on.

 

[Prismatic]

Because we have to decide if the change in data is real or spurious. The only dependable method is to note that the spurious changes are too large to be physical, and so the test is to compare with the previous data point.


It's the threshold set to determine if the change was too large.


Yes they are. The wave declaration is required to declare that data_wave is a wave. The WaveStats function generates, amongst other things, the standard variable V_npnts which is used to close the do loop.


No - it's an output result for the wave that WaveStats operated on.

Good info, thanks! I was guessing, as I am unfamiliar with the language. (My Master’s was largely about the design of programming languages, but that’s of limited use when given just a short snippet of code. ?)

 

[sar104]

Good info, thanks! I was guessing, as I am unfamiliar with the language. (My Master’s was largely about the design of programming languages, but that’s of limited use when given just a short snippet of code. ?)

Apologies - I should have annotated it but it was really included just for anyone currently using Igor Pro.

 

[Chanctonbury]

Such talented analysis of the corrupted data - I am in awe! I hope I never have to ask for this kind of help from the group but it is very reassuring that such help is available.....

 

[RodPad]

@Chanctonbury,
Welcome to the Forum!

Please make a post here.
Pilot Check In
Add what bird you are flying, or you want to.

Rod

 

[KennyL]

I think I've seen a similar case once before. So it's probably quite rare. I doubt that CsvView can fix it since it requires a somewhat customized signal processing. As it happens I first developed simple functions to fix those kinds of errors some years ago, when a bug in some Tektronix digitizers caused similar random offset issues. I was programming and controlling the digitizers with Igor Pro, and the same basic approach works for these data.

Sar104 - - you amaze me !!!!
how you can figure all this out is mind blowing
You helped me out explaining a crash I had in the past
Thanks much for your time with this group !

 

[Azarov]

Afternoon everyone - a bit of help if possible please.

Took my Mavic Mini and decided to fly it near to a Loch (I think you can guess where this is heading!). i was flying it above the church next to the Loch and it lost signal and went into some kind of fail safe mode, only had the drone since Christmas so I am not fully up to speed with the terminology etc yet :-/

Anyway, I lost sight of the drone, above some trees and after several minutes the screen on my remote was still saving that it had lost signal. I ran around searching for the drone, aiming the remote at the sky where the drone roughly was, but with no luck. After assuming that he drone was going to land directly below where it was flying, I searched for approx 45 minutes before checking that the drone had in fact flown in a straight line over the Loch and ended up 600m from the homepoint at the to bottom of the Loch, I was unable to attempt to recover the drone.

What are my options? I honestly believe that it was not my fault that the drone did this, the wind was not that strong at all and was was actually going the opposite direction to where the drone ended up, so the drone actually flew into the wind to where it ended up. I have seen that people can access the flight log etc to see if any errors occurred and to prove that this was a drone malfunction as opposed to pilot error so to speak.

Any help much appreciated.

Cheers
Sam

First thing I did when got my new drone, I insured it. DJI offering insurance but I found a better deal with my Insuarance company. In case of an incident they're asking only for a proof of purchase.

Trees are not blocking RF signal. However I don't know the max flying distance for Mavic Mini. Mavic 2 Pro is 18 km.

Mavic 2 Pro has an option RTH in case of signal lost.

 

[Renoetra]

First thing I did when got my new drone, I insured it. DJI offering insurance but I found a better deal with my Insuarance company. In case of an incident they're asking only for a proof of purchase.

Trees are not blocking RF signal. However I don't know the max flying distance for Mavic Mini. Mavic 2 Pro is 18 km.

Mavic 2 Pro has an option RTH in case of signal lost.

The mavic mini has also this feature.

 

[Chanctonbury]

@Chanctonbury,
Welcome to the Forum!

Please make a post here.
Pilot Check In
Add what bird you are flying, or you want to.

Rod

Thanks, Rod, I have checked in as you suggest.

 

[Prismatic]

First thing I did when got my new drone, I insured it. DJI offering insurance but I found a better deal with my Insuarance company. In case of an incident they're asking only for a proof of purchase.

Trees are not blocking RF signal. However I don't know the max flying distance for Mavic Mini. Mavic 2 Pro is 18 km.

Mavic 2 Pro has an option RTH in case of signal lost.

Just a small but important point: trees definitely can and do impede the RF signals between the AC and RC. Flying above a dense canopy of vegetation that you're standing under drastically reduces your range. It's actually the water in the plant that causes this, so forests of bare trees have less effect than those with lots of juicy leaves.

 

[Drones.n.Pixels]

We have all been there : The learning curve

Without seeing the Data Sheets it appears your Drone lost signal when you went over the trees as you Lost Visual Line of sight something that is extremely important in keeping the signal connected .

When that happens over the trees the best thing to do is fly the drone up high in the sky to try to reconnect.

When the GPS is completely lost the Drone goes into Atti Mode which means that you have lost the help of the GPS and you our now flying in Somewhat Manually. which also means the wind has some control if you do not .

There is no harm in notifying DJI but this is Pilot Error.

VLOS plays a critical role in keeping the drone connected to the GPS to allow it to use its safety features..

DJI will ask you for the data and the video recorded on the Cashe so be prepared and if they find some errors in the Atti Mode you might be ok or they find some magentic interference also which can cause a fly away.

Phantomrain.org
Gear to fly your Mavic in the Rain.
Coal

Doesn't Mavic Mini have in-flight GPS? If it does, VLOS (or losing it) has nothing to do with loss of GPS. this might be pilot error (most fly-aways actually are), but without logs it's impossible to say.
If the drone lost GPS, if flew with the wind and landed when battery wend down to critical level. Without GPS it cannot come back. Unfortunately loss o GPS can happen without failure of the actual equipment.
To save the drone, pilot must be able to land it safely where it can be found (if compass is working this can be done using the map) or brought back manually in ATTI mode (also using the map).
It's scary and not easy (happened to me with my MP), especially if you don't see the drone and don't trust the controls any more.

 

[Prismatic]

Doesn't Mavic Mini have in-flight GPS? If it does, VLOS (or losing it) has nothing to do with loss of GPS. this might be pilot error (most fly-aways actually are), but without logs it's impossible to say.
If the drone lost GPS, if flew with the wind and landed when battery wend down to critical level. Without GPS it cannot come back. Unfortunately loss o GPS can happen without failure of the actual equipment.
To save the drone, pilot must be able to land it safely where it can be found (if compass is working this can be done using the map) or brought back manually in ATTI mode (also using the map).
It's scary and not easy (happened to me with my MP), especially if you don't see the drone and don't trust the controls any more.

You should have finished reading the thread, particularly the log file analysis in this post., which would have been impossible but for the unique skills of @sar104.

Synopsis: The drone never lost GPS. At a high altitude in considerable wind, RTH was inadvertently cancelled. The drone drifted downwind until the link was lost. The wind made failsafe RTH futile, and it continued drifting away. While it probably made landfall across the loch, the OP does not live nearby; recovery is conceivable, but not likely.

 

[SamCrouch]

Is this the actual flight location @SamCrouch ??
If you weren't on holiday up there, it is probably a bit far north for you !

Hi, yep that is the exact location!