Missing telemetry when signal lost

[Costas Masalas]

I fly a Mavic Pro Platinum using Litchi to do some autonomous flights.

Today I experienced a signal lost in my flight. The longest distance from take off was 2.400m. Signal lost was at 2.000m. The mission continued as planned. When the drone was returning I regained signal at 2.000m.

Finished the mission as planned but when I check the airdata telemetry I get details only for these 2km but I do not have any for the 400m that the drone was flying alone without signal to the controller (and Litchi).

(I think this happened again 1 more time in the past.)

I have experienced in the past a few times some signal lost but I had the telemetry for the whole flight.

Is the telemetry recorded live on the phone and then to airdata or the telemetry is recorded to the drone and then transferred to the phone and then to airdata?
Is there a time limit for how long time it takes to regain signal before you lose some of the telemetry?
It's there a setting that I need to change?

I ask because the telemetry files on the phone that are in .srt format at very basic and I thought that the very detailed telemetry that we get with airdata should come and record in the drones internal memory. If that is the case the drone should record data even with no signal and upload that when signal is back on.

I'm sure that in the past I had no such problem. Is there something changed in the recent updates in DJI 4 app and Litchi?

I fly the drone professionally and my missions require to fly in long distances in perfect strait lines and in very rough terrain. Thus as much careful planning I can do there will unavoidable be some cases with signal lost. These telemetry files are very important for the missions I do.

Please advise.
Thank you for your time in advance.

[Airdata UAV]

Hi, 

We just sent you an offline email about this.

Thanks, 

Frederic

[Costas Masalas]

Thank you for your answer.

The thing i do not understand (and i do not know if something is changed) is that in the past i experienced signal lost for some minutes during flight but i get all telemetry info even for the part that i had no signal to the drone.

eg. for you to investigate check the following flights.

1) -> 10-05-2018 13:17:15 (i had no connection to the drone from point C throughout to point U BUT i had the telemetry data just fine)

2) -> 10-05-2018 13:17:15 (I had no connection to the drone in this flight at a specific area and the drone did 3 passes through it BUT still i get the telemetry)

These are two cases with a severe lost signal BUT i still have all telemetry. Why?

What is different than my last flight?

[Airdata UAV]

Hi Costas,

Thanks for the note.

We had a look at your flight (10-05-2018 13:17:15) and we can see that you are losing the signal and getting back so a new file is not create and Airdata is able to connect the dots between each loss of signal.

The Downlink data connection lost (Data Loss) means that the remote got partial or no flight data from the aircraft for more than 1 second, which means the data downlink had issues. 

This is a known issue when flying missions and losing connection during the flight - the path will only display the details from when the signal was available.

Hope this helps. 

Best regards,

Frederic

[Mark & Lyndon]

Costas, I too have dealt with this issue for months now.  Your only immediate recourse is to pull the flight data file(s) down directly from your Mavic (using extractDJI app) and then use datcon app to extract flight data files and create csv files with total flight data telemetry in them. It is a tedious process but it works and is a big learning curve.

Months ago I asked Airdata about this exact thing and they told me back then they were looking into using the flight telemetry data from the Mavic but it never happened and I now strongly suspect they were just feeding me a line.  I hope I'm wrong. I signed up with one of their plans hoping that if/when that became real, the plan I'm paying for would cover it, but again, don't think it's a reality.  But, you can do this, you just need to get saavy on what I mentioned.

[Costas Masalas]

On Monday, 2 July 2018 23:19:27 UTC+3, Airdata UAV wrote:

Hi Costas,

Thanks for the note.

We had a look at your flight (10-05-2018 13:17:15) and we can see that you are losing the signal and getting back so a new file is not create and Airdata is able to connect the dots between each loss of signal.

The Downlink data connection lost (Data Loss) means that the remote got partial or no flight data from the aircraft for more than 1 second, which means the data downlink had issues. 

This is a known issue when flying missions and losing connection during the flight - the path will only display the details from when the signal was available.

Hope this helps. 

That is weird because i'm sure that i had to connection at all for a couple on minutes. Maybe there was some weak signal as you say that i'm not aware of that was able to transfer telemetry log. In any way i could not communicate with my drone and issue commands in any possible way for that time.

Thanks again for your information and i hope that you integrate in your site telemetry data taken from the Drone's internal memory. That is the best and more fail-safe approach.

[Costas Masalas]

Hello Mark & Lydon.

I have another problem right now with the method you said.

I had DJI's Assistant 2 on my PC and was working fine. I also had my PC for years without a clean install and recently i got a big job so i decided to format my PC.

After formatting my PC and clean installing Windows 10 Pro i install DJI Assistant 2 but i am not able to login because i do not get the notification code that is required to login. (i get a broken image instead of a code) Thus i'm not able to connect my Drone to PC to retrieve data logs. I cannot upgrade firmware that way and any other feature that you get with Assistant 2. I also have the same problem on a 2nd PC at the office.

Many people had this problem in a lot of forums that i checked but no solution. I contacted DJI twice and they do not know anything. They just said that they communicate with the developers and that they will contact me for a solution. To no avail. They never contacted me. I also asked for a past version of the program (v1.0.7) because some people had success with that and then they could upgrade to the newest version but DJI did not helped in that either.

So thank you for your suggestion my friend but in my situation even that it is not an option.

[tiborvar]

I have recently tested "Failsafe RTH" on my Phantom 4 RTK.
I turned off the RC when the drone was about 90m away. It beheaved as expected: rised to preset RTH-altitude after a few seconds , returned to HomePoint and performed a flawless Auto Landing.

I was surprised when I looked at the log on airdata.com. There was no record of "loss of RC-signal" neither was there a track of the return flight path.

Do I have to fetch the *.DAT file to have that information ?

--
regards
Tibor

[tre...@airdata.com]

Hi Tibor, 

Thanks for the question. When you conduct a flight, the flight app being used (GO 4, Litchi, etc.) creates a .TXT flight record - additionally, the drone creates a .DAT record. We typically recommend that you upload the .TXT records, as they are much small than the .DAT files and can be automatically uploaded, most of the time. Seeing as how you were likely viewing the .TXT record, it makes sense that the segment where your RC was shut off is not showing as there was no connection between the drone and RC for that duration. 

Feel free to upload the .DAT file, which will show the flight tracks for the entire flight. The .DAT file is retrieved from the aircraft using DJI's Assistant 2 software, and can be uploaded to AirData here: https://app.airdata.com/main?a=upload

Best, 

Trevor 

[tiborvar]

It would be cool if the RC could interrogate the aircraft after the next power up: "Where have you been without telling me first ?"  ;-)

—

Tibor

man. 10. mai 2021 kl. 19:54 skrev tre...@airdata.com <tre...@airdata.com>:

Hi Tibor, 

Thanks for the question. When you conduct a flight, the flight app being used (GO 4, Litchi, etc.) creates a .TXT flight record - additionally, the drone creates a .DAT record. We typically recommend that you upload the .TXT records, as they are much small than the .DAT files and can be automatically uploaded, most of the time. Seeing as how you were likely viewing the .TXT record, it makes sense that the segment where your RC was shut off is not showing as there was no connection between the drone and RC for that duration. 

Feel free to upload the .DAT file, which will show the flight tracks for the entire flight. The .DAT file is retrieved from the aircraft using DJI's Assistant 2 software, and can be uploaded to AirData here: https://app.airdata.com/main?a=upload

Best, 

Trevor 

--

med vennlig hilsen
Tibor Vári

[tre...@airdata.com]

Hi Tibor, 

You're right, it would be helpful if the RC could ask the drone such questions, wouldn't it? :) 

Best, 

Trevor