Interpreting failed Litchi Mission AirData info

[LZJ]

Okay, wondering if anyone can help me with this. Attempted a Litchi Mission with Ph4p that failed about 1/4 of the way into the mission. When it did my controller indicated that it lost satellites. Check out the Airdata link that shows the drone stalling/hovering toward the end of record (click the "notifications" tab at the top of the map and then click the "High Definition Flight player" tab immediately above or below the map:


I find it interesting that according to the Airdata log it never lost more than 9 satellites. When this happened it stopped as shown in the link and apparently either I inadvertently switched to P mode from waypoint mode or the drone did on its own. The drone stopped and hovered. RC screen had a GPS signal error and GPS data error. I had video but despite it apparently being in P mode I could not move it. I don't honestly remember if the mode change was reflected on the controller or not. I do not recall flipping the manual mode switch either. Attempted multiple RTHs by the RC button but as you can see from the log it didn't work. Notice the speed drop from 11.4 mph to 0, the "deviation" change from .0008 to .0009 (anyone have any idea what this means or reflects???) and mode change from waypoint to P. Finally after what seemed like 10 minutes I could move the drone and was able to fly it back to the take off point during which the RC indicated 0 satellites. Really scary part was RTH failed despite multiple attempts. Also weird that AirData quit logging any data when I was able to move the drone and manually start to fly it back to the home point. The RC indicated the drone had 0 satellites on the manual flight home until I was able to land it, restart the RC and restart the drone and it then found satellites again... Any idea of a direction to go in with this? Thanks

 

[crash1sttime]

If it stopped logging, have a look for a second log file for the same time date, if the controller loses connection to the drone it will stop logging and then start a new log when it reconnects

Im also interested in why this is shown, why did your battery drop to such a low count at 12mins into the flight

12m 08s

114.5 ft

0.41 mi

40% Battery

 

[Meta4]

I find it interesting that according to the Airdata log it never lost more than 9 satellites.

The recorded data shows the number of sats dropping to zero briefly a few times after 261 seconds.
And after 296 seconds it drops to zero and stays on zero for the rest of the flight.

The maximum number of sats acquired was only 13, which is very low for a P4 pro, which typically finds 20+ sats when flown out in the open.

When this happened it stopped as shown in the link and apparently either I inadvertently switched to P mode from waypoint mode or the drone did on its own

It had nothing to do with switching flight modes.

I attempted multiple RTHs by the RC button but as you can see from the log it didn't work. Notice the speed drop from 11.4 mph to 0, the "deviation" change from .0008 to .0009 (anyone have any idea what this means or reflects???) and mode change from waypoint to P.

Without GPS, the drone has no location information.
Litchi cannot work without location data and the speed comes from GPS.

Finally after what seemed like 10 minutes I could move the drone and was able to fly it back to the take off point during which the RC indicated 0 satellites. Really scary part was RTH failed despite multiple attempts. Also weird that AirData quit logging any data when I was able to move the drone and manually start to fly it back to the home point. The RC indicated the drone had 0 satellites on the manual flight home until I was able to land it, restart the RC and restart the drone and it then found satellites again... Any idea of a direction to go in with this?

Find out if it was a one-off glitch or if you have a real problem with GPS reception.
If the problem continues, you probably need to fix the GPS antenna connection, or replace the GPS antenna.

 

[LZJ]

If it stopped logging, have a look for a second log file for the same time date, if the controller loses connection to the drone it will stop logging and then start a new log when it reconnects

Im also interested in why this is shown, why did your battery drop to such a low count at 12mins into the flight

12m 08s

114.5 ft

0.41 mi

40% Battery

Where did you find the 12 min data? I can only see it through 4+ mins or so....

 

[LZJ]

The recorded data shows the number of sats dropping to zero briefly a few times after 261 seconds.
And after 296 seconds it drops to zero and stays on zero for the rest of the flight.

The maximum number of sats acquired was only 13, which is very low for a P4 pro, which typically finds 20+ sats when flown out in the open.

It had nothing to do with switching flight modes.

Without GPS, the drone has no location information.
Litchi cannot work without location data and the speed comes from GPS.

Find out if it was a one-off glitch or if you have a real problem with GPS reception.
If the problem continues, you probably need to fix the GPS antenna connection, or replace the GPS antenna.

Great points. Where or how did you see or find the 0 satellite data? I don't see it in the log??

 

[Meta4]

Great points. Where or how did you see or find the 0 satellite data? I don't see it in the log??

The actual recorded data shows much more than Airdata's brief summary.

 

[LZJ]

I'm sure that is true. But how do I open it or find it? Thanks

 

[Meta4]

I'm sure that is true. But how do I open it or find it? Thanks

Click the CSV link that's below the map image on the Overview page of your Airdata report.

 

[LZJ]

Click the CSV link that's below the map image on the Overview page of your Airdata report.

Thanks. I didn't realize that had more detailed data. Very good. Thank you again.

 

[LZJ]

Thanks. I didn't realize that had more detailed data. Very good. Thank you again.

Okay, So I replaced both antennas and antenna cables on my php 4 and did another test flight in which the dat file shows a couple of events in which it completely lost all satellite connections to 0 at which time the log file documents a recurrent error line of: [L-GPS]<GPS Error>m8_check_hash_failed[1] gps [0][0]|| anyone have any idea what this means? Than

 

[Starz]

Antennas in the legs are different than the gps module if I’m understanding your post.
Did you replace the gps module? The gps module can fail or possibly a connector that has failed. There are two connectors that make up that part of the system. One on the module itself, and one where it connects to the main board. Short cable in between the two points.

 

[BudWalker]

Okay, So I replaced both antennas and antenna cables on my php 4 and did another test flight in which the dat file shows a couple of events in which it completely lost all satellite connections to 0 at which time the log file documents a recurrent error line of: [L-GPS]<GPS Error>m8_check_hash_failed[1] gps [0][0]|| anyone have any idea what this means? Than

No idea what this entry means - except that it's about the GPS system. The entries in the eventLog stream are mostly debug statements used by DJI engineers. As such they are only occasionally useful to us non DJI engineers. Often these entries describe some problem that has no material adverse effect.

As @Meta4 said GPS data can be seen in the .csv produced by AirData from the .txt log. Looks like you are also looking at the .DAT. The .csv created from the .DAT will also contain GPS data.

As @Starz suggested the GPS system has multiple components that can fail. Seems you've eliminated the antennas themselves. That leaves the connectors and GPS module. Neither the .txt or .DAT log will have data that can be specific about where the problem lies. From the looks of it I would suspect a loose or faulty connection.

 

[LZJ]

No idea what this entry means - except that it's about the GPS system. The entries in the eventLog stream are mostly debug statements used by DJI engineers. As such they are only occasionally useful to us non DJI engineers. Often these entries describe some problem that has no material adverse effect.

As @Meta4 said GPS data can be seen in the .csv produced by AirData from the .txt log. Looks like you are also looking at the .DAT. The .csv created from the .DAT will also contain GPS data.

As @Starz suggested the GPS system has multiple components that can fail. Seems you've eliminated the antennas themselves. That leaves the connectors and GPS module. Neither the .txt or .DAT log will have data that can be specific about where the problem lies. From the looks of it I would suspect a loose or faulty connection.

Antennas in the legs are different than the gps module if I’m understanding your post.
Did you replace the gps module? The gps module can fail or possibly a connector that has failed. There are two connectors that make up that part of the system. One on the module itself, and one where it connects to the main board. Short cable in between the two points.

Yes, I replaced both antennas/legs using new connection cables but I have not replaced the GPS module yet. Thinking of doing that and the main power board. The cable from the GPS module to the power board looks seated fine.

 

[Starz]

Main power board probably isn’t the issue.
Did you split the shell to view the gps cable?

 

[LZJ]

Main power board probably isn’t the issue.
Did you split the shell to view the gps cable?

Yes. Cable was kinked but otherwise seemed okay. Now I wonder.