Post Flight Briefing Question

[StubbornSwiss]

Greetings!

On a flight this afternoon, I experienced a RC signal loss for more than 11 seconds, resulting in the drone initiating a Failsafe RTH. Everything worked as it was supposed to, and after a few moments, and after I re-oriented the antenna towards the drone, signal was restored and I was able to continue with my flight. I pretty much knew exactly what was happening, let the drone do its thing, and observed as it all played out. It was actually quite a good experience. If you do your part (make sure you have required sats, set home point properly, make sure compass is functioning properly, etc), these little machines are actually very smart!

That being said, I do have a question as to something I noticed during my post flight briefing.

Here is a link to the data for this flight on the AirdataUAV site:

AirdataUAV Log

Looking at the General > Notifications tab, we see that at 5m 40s the Downlink had been lost for 13.3 secs, and the drone then initiated a failsafe RTH. Right after this, still at 5m 40s we see a warning for “No GPS signal”. However, going to the Sensors > GPS tab, we see that throughout the flight the Lowest Satellite Count was 10, and nowhere else do I see any indication of loss of GPS.

So my question is this. What exactly was that “No GPS signal” warning?

Would appreciate any insight from the more knowledgeable members.

Cheers!

 

[old man mavic]

its just telling you that it entered ATTI mode because at that moment it did not have enough sats locked,due to something blocking the signal to the GPS module

 

[sar104]

It looks like the aircraft lost navHealth while disconnected, but without access to the txt log that's just speculation.

 

[StubbornSwiss]

its just telling you that it entered ATTI mode because at that moment it did not have enough sats locked,due to something blocking the signal to the GPS module

Thanks for your response, OMM, but I do find that rather difficult to understand. At that time period, I had 14 or more sats (look at the Sensors > GPS tab). Also wouldn't it have indicated that it was going into Atti mode? If it did go into Atti mode, wouldn't this have cancelled the RTH?

 

[StubbornSwiss]

It looks like the aircraft lost navHealth while disconnected, but without access to the txt log that's just speculation.

Hey sar104...... thanks for getting onboard. Can I just upload the .txt file here?

 

[old man mavic]

it was more of a glitch and could have been due to interference around the time you lost signal Sar104 is the person to ask

 

[StubbornSwiss]

it was more of a glitch and could have been due to interference around the time you lost signal Sar104 is the person to ask

Yup...... I was thinking the same - glitch, but just wanted to make sure. A lot of interference around that time! (I need to be careful not to push my luck).

 

[Meta4]

Yup...... I was thinking the same - glitch, but just wanted to make sure. A lot of interference around that time! (I need to be careful not to push my luck).

There was no glitch, no interference to GPS, no GPS problem at all.
Just Airdata giving you false information.
At the time, the drone was 260 feet up with 19 sats locked and GPS Health was registering at 5/5

 

[StubbornSwiss]

There was no glitch, no interference to GPS, no GPS problem at all.
Just Airdata giving you false information.
At the time, the drone was 260 feet up with 19 sats locked and GPS Health was registering at 5/5

Excellent. Thanks a lot for this @Meta4

Was this data extracted from the .txt file, and if so using what software?

Again, many thanks!

 

[Meta4]

Was this data extracted from the .txt file, and if so using what software?

It was in the txt file which is the actual data rather than Airdata's summary.
I used the excellent Phantomhelp log viewer DJI Flight Log Viewer | Phantom Help
If you open up the CSV spreadsheet you can see GPS data for every 1/10th of a second of the flight.

 

[StubbornSwiss]

It was in the txt file which is the actual data rather than Airdata's summary.
I used the excellent Phantomhelp log viewer DJI Flight Log Viewer | Phantom Help
If you open up the CSV spreadsheet you can see GPS data for every 1/10th of a second of the flight.

Ok great. I really like to understand what is going on with my drone, but up till now I've just been using Airdata. I will definitely now start using Phantomhelp log viewer, as it appears Airdata does not always accurately interpret the log data.

Thanks again.

 

[sar104]

It was in the txt file which is the actual data rather than Airdata's summary.
I used the excellent Phantomhelp log viewer DJI Flight Log Viewer | Phantom Help
If you open up the CSV spreadsheet you can see GPS data for every 1/10th of a second of the flight.

Ok great. I really like to understand what is going on with my drone, but up till now I've just been using Airdata. I will definitely now start using Phantomhelp log viewer, as it appears Airdata does not always accurately interpret the log data.

Thanks again.

Actually the warning was real, in the sense that it occurred. The warnings posted to the app are recorded in the txt log, and AirData is simply reading them:

0.0 0.0 IN FLIGHT0​

0.0 0.3 2.2 1HOMEPOINT UPDATED. RTH ALTITUDE ADJUSTED TO 98 FT!​

5.2 116.2 133.2 1HOMEPOINT UPDATED. RTH ALTITUDE ADJUSTED TO 98 FT!​

136.2 312.3 2FPV_NFZ_BEFORE_TAKEOFF_IN_NFZ_IN_WARNING_AREA_TIPS4AIRCRAFT IN WARNING ZONE (AIRPORT). FLY WITH CAUTION!​

317.4 323.1 IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)​

323.1 AIRCRAFT SIGNAL INTERFERENCE​

323.6 IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

326.0 :REMOTE CONTROLLER DISCONNECTED FROM AIRCRAFT (CODE: 30029)IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

326.0 RC SIGNAL LOST​

326.0 REMOTE CONTROLLER SIGNAL LOST!​

327.0 :REMOTE CONTROLLER DISCONNECTED FROM AIRCRAFT (CODE: 30029)NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

327.0 327.0 AIRCRAFT NOT CONNECTED TO RC​

340.3 GNO GPS SIGNAL. AIRCRAFT UNABLE TO HOVER. FLY WITH CAUTION (CODE: 30008)​

340.3 TAKE OFF WITH CAUTION (NO GPS)​

340.5 340.5 IN FLIGHT0​

340.8 341.7 RETURNING TO HOME0​

347.3 2FPV_NFZ_BEFORE_TAKEOFF_IN_NFZ_IN_WARNING_AREA_TIPS4AIRCRAFT IN WARNING ZONE (AIRPORT). FLY WITH CAUTION!​

352.3 355.8 NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

355.8 WEAK SIGNAL. ADJUST ANTENNAS​

356.1 IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

356.1 AIRCRAFT SIGNAL INTERFERENCE​

356.9 IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)​

359.1 359.1 RETURNING TO HOME0​

360.0 IN FLIGHT0​

434.2 /FPV_TIPS_NFZ_FLYING_TOUCH_HEIGHT_LIMIT_ZONE_TOP-MAX ALTITUDE REACHED (ALTITUDE LIMIT: 305 FT)!​

439.4 445.7 2FPV_NFZ_BEFORE_TAKEOFF_IN_NFZ_IN_WARNING_AREA_TIPS4AIRCRAFT IN WARNING ZONE (AIRPORT). FLY WITH CAUTION!​

450.7 499.2 /FPV_TIPS_NFZ_FLYING_TOUCH_HEIGHT_LIMIT_ZONE_TOP-MAX ALTITUDE REACHED (ALTITUDE LIMIT: 305 FT)!1​

504.3 542.1 IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)​

542.1 AIRCRAFT SIGNAL INTERFERENCE​

544.8 IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

544.9 NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

544.9 WEAK SIGNAL. ADJUST ANTENNAS​

546.5 546.5 IN FLIGHT0​

627.2 /FPV_TIPS_NFZ_FLYING_TOUCH_HEIGHT_LIMIT_ZONE_TOP-MAX ALTITUDE REACHED (ALTITUDE LIMIT: 305 FT)!​

632.3 OK​

That said, there really did not appear to be much problem with the GPS data, so the cause of the warning is a bit of a mystery. It appeared after the connection was restored following 13 seconds of signal loss, and since we don't know what happened during those 13 seconds it is impossible to pin down further.

 

[StubbornSwiss]

Actually the warning was real, in the sense that it occurred. The warnings posted to the app are recorded in the txt log, and AirData is simply reading them:

0.0 0.0 IN FLIGHT0​

0.0 0.3 2.2 1HOMEPOINT UPDATED. RTH ALTITUDE ADJUSTED TO 98 FT!​

5.2 116.2 133.2 1HOMEPOINT UPDATED. RTH ALTITUDE ADJUSTED TO 98 FT!​

136.2 312.3 2FPV_NFZ_BEFORE_TAKEOFF_IN_NFZ_IN_WARNING_AREA_TIPS4AIRCRAFT IN WARNING ZONE (AIRPORT). FLY WITH CAUTION!​

317.4 323.1 IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)​

323.1 AIRCRAFT SIGNAL INTERFERENCE​

323.6 IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

326.0 :REMOTE CONTROLLER DISCONNECTED FROM AIRCRAFT (CODE: 30029)IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

326.0 RC SIGNAL LOST​

326.0 REMOTE CONTROLLER SIGNAL LOST!​

327.0 :REMOTE CONTROLLER DISCONNECTED FROM AIRCRAFT (CODE: 30029)NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

327.0 327.0 AIRCRAFT NOT CONNECTED TO RC​

340.3 GNO GPS SIGNAL. AIRCRAFT UNABLE TO HOVER. FLY WITH CAUTION (CODE: 30008)​

340.3 TAKE OFF WITH CAUTION (NO GPS)​

340.5 340.5 IN FLIGHT0​

340.8 341.7 RETURNING TO HOME0​

347.3 2FPV_NFZ_BEFORE_TAKEOFF_IN_NFZ_IN_WARNING_AREA_TIPS4AIRCRAFT IN WARNING ZONE (AIRPORT). FLY WITH CAUTION!​

352.3 355.8 NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

355.8 WEAK SIGNAL. ADJUST ANTENNAS​

356.1 IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

356.1 AIRCRAFT SIGNAL INTERFERENCE​

356.9 IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)​

359.1 359.1 RETURNING TO HOME0​

360.0 IN FLIGHT0​

434.2 /FPV_TIPS_NFZ_FLYING_TOUCH_HEIGHT_LIMIT_ZONE_TOP-MAX ALTITUDE REACHED (ALTITUDE LIMIT: 305 FT)!​

439.4 445.7 2FPV_NFZ_BEFORE_TAKEOFF_IN_NFZ_IN_WARNING_AREA_TIPS4AIRCRAFT IN WARNING ZONE (AIRPORT). FLY WITH CAUTION!​

450.7 499.2 /FPV_TIPS_NFZ_FLYING_TOUCH_HEIGHT_LIMIT_ZONE_TOP-MAX ALTITUDE REACHED (ALTITUDE LIMIT: 305 FT)!1​

504.3 542.1 IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)​

542.1 AIRCRAFT SIGNAL INTERFERENCE​

544.8 IAIRCRAFT IN HIGH INTERFERENCE ENVIRONMENT. FLY WITH CAUTION (CODE: 80015)NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

544.9 NREMOTE CONTROLLER SIGNAL WEAK. ADJUST REMOTE CONTROLLER ANTENNAS (CODE: 80002)​

544.9 WEAK SIGNAL. ADJUST ANTENNAS​

546.5 546.5 IN FLIGHT0​

627.2 /FPV_TIPS_NFZ_FLYING_TOUCH_HEIGHT_LIMIT_ZONE_TOP-MAX ALTITUDE REACHED (ALTITUDE LIMIT: 305 FT)!​

632.3 OK​

That said, there really did not appear to be much problem with the GPS data, so the cause of the warning is a bit of a mystery. It appeared after the connection was restored following 13 seconds of signal loss, and since we don't know what happened during those 13 seconds it is impossible to pin down further.

View attachment 100349

Thanks sar104, I really appreciate this. Interesting stuff this. I must spend some time getting a better understanding of the data.

Ok.... so if the drone is disconnected from the RC, it means for the period of disconnection there is no data written to the .txt file, since the .txt file resides on the RC. Understood.
How about the .dat file? That resides on the drone, so would one be able to glean any more relevant data from that file?

Sorry for my ignorance..... this is an area I'm only just now trying to learn.

 

[StubbornSwiss]

Double Post. Please delete

 

[sar104]

Thanks sar104, I really appreciate this. Interesting stuff this. I must spend some time getting a better understanding of the data.

Ok.... so if the drone is disconnected from the RC, it means for the period of disconnection there is no data written to the .txt file, since the .txt file resides on the RC. Understood.
How about the .dat file? That resides on the drone, so would one be able to glean any more relevant data from that file?

Sorry for my ignorance..... this is an area I'm only just now trying to learn.

Data continue to be written to the DAT file on the aircraft, but on the Mini that's only readable by DJI. The DAT file on the mobile device will have the same data gap as the txt log.

 

[StubbornSwiss]

Data continue to be written to the DAT file on the aircraft, but on the Mini that's only readable by DJI. The DAT file on the mobile device will have the same data gap as the txt log.

I didn't know a .dat file was also recorded to the device. So if there is no disconnection during a flight, is the data recorded to the .dat file on the drone the same as the one on the device? Is the .dat file on the device also deleted when the flight logs are synced to the DJI server?

A lot to learn still!

Thank you.

 

[StubbornSwiss]

Quick question.........

In playing back a flight on Phantom Log Viewer, is there a way to play through the flight without having to keep tapping the right arrow key?

Thanks.

 

[sar104]

I didn't know a .dat file was also recorded to the device. So if there is no disconnection during a flight, is the data recorded to the .dat file on the drone the same as the one on the device? Is the .dat file on the device also deleted when the flight logs are synced to the DJI server?

A lot to learn still!

Thank you.

The DAT file on the mobile device records a lot more data types than the txt log, but still less than the aircraft DAT file and at a lower data rate. It's the mobile device DAT file that is deleted when the records are synchronized with the DJI servers - the txt log and aircraft DAT file are not deleted.

The log retrieval guide has more detailed explanations:

Mavic Flight Log Retrieval and Analysis Guide

With the introduction of the Mavic Mini there has been a noticeable uptick in the number of posts requesting help with lost or crashed aircraft. While there is plenty of help and advice available on this forum, and detailed guidance and options on several other websites, I thought that perhaps a...

mavicpilots.com

 

[StubbornSwiss]

Thank you so much for sorting that out for me. I appreciate it.

And as you said, the .DAT file from the aircraft is only readable by DJI (for the MM).

I'll go back and read over the log retrieval guide again.

Thanks again.