P4P with Litchi waypoints

[pelleplutt]

Hi all!
Since I started drone flying two months ago I made several Litchi waypoint missions without problems. Longest one was 2,2 km with 15 waypoints. A few weeks ago I made a quite simple mission in Virtual Litchi Mission, with a few waypoints, less than 1 km in total, at two minutes run time.
I always try to be careful from start, going through the mission several times, checking that every parameter in VLM is correct. Also always check with DJI Go 4 that everything is ok, and then close that app.
I started controller, drone, and finally Litchi, taking good time for everything to stabilize. Loaded the mission, first WP WP #1, got the "starting point updated" message, checked the map, 8 satellites present, GPS navigation, all looked fine. Pressed Start, the drone rose to 10 meters, made a 90° turn to the left (which was wrong), and flew straight into a pine tree behind me. Then I am not sure how I reacted but after two seconds the drone came out from the tree and returned to previoius point above starting point. By then I had switched to S mode (according to log I also managed to switch to A mode) and brought the drone down manually. Puh, no damage.
I have studied (or at least tried to) the flight log on Airdata. As you can see from images below, the flight was not as intended.

View attachment 122350View attachment 122351
A few additional comments:
- Log says GPS signal was weak. Can that be the case when 8 satellites are detected?
- Since camera was pointing towards the shore during entire mission, this time I placed the drone with the back towards WP #1. Could that be an explanation?

Anyone has any clue to what went wrong?

 

[Meta4]

Anyone has any clue to what went wrong?

Not without seeing any data and your Litchi flight plan.

 

[MapMaker53]

Some sort of metal interference in the takeoff surface? Was there any compass error warning? Satellite count can drop in and out as the amount of viewable sky changes. Launching close to a forested area or structure could block half the sky. Just throwing some thoughts out there. Taking off in the wrong direction on a WP mission seems to me to be a compass issue. Could you have accidentally launched the WP mission in Atti mode? I've never done that and do not know how the drone might act.

 

[pelleplutt]

Some sort of metal interference in the takeoff surface? Was there any compass error warning? Satellite count can drop in and out as the amount of viewable sky changes. Launching close to a forested area or structure could block half the sky. Just throwing some thoughts out there. Taking off in the wrong direction on a WP mission seems to me to be a compass issue. Could you have accidentally launched the WP mission in Atti mode? I've never done that and do not know how the drone might act.

Thanks Meta4, not sure what happened to attached images, they were there when creating this post. Now its only links which does not open.
And thanks MapMaker53. No metal, no compass warning.

Attaching images again which hopefully will answer your questions.

 

[Meta4]

Thanks Meta4, not sure what happened to attached images, they were there when creating this post.

A pic of one of the Airdata pages isn't much help.
Can you share the Airdata report so that the actual data can be looked at?

 

[pelleplutt]

Hope you can access this

 

[Meta4]

Log says GPS signal was weak. Can that be the case when 8 satellites are detected?

According to the flight data the number of satellites was 7-9 for most of the flight and briefly touched 10 and 11.
But the number of satellites is not what's important.
The drone also needs the satellites to be spread well over the sky.
Your drone's GPS Health never changed from 0/5. (hence the weak GPS message)
It needs to be 4 or 5 before the flight controller accepts the data.
Your drone never went into GPS mode and never recorded a home point.
So it had no horizontal position holding and was never ready to start the mission.

Before launching for a waypoint mission, it is essential that you wait for the app to advise that the home point is recorded and the drone is in P-GPS mode.

 

[pelleplutt]

Thanks a lot Meta4 for taking your time!

I won't argue with an experienced drone aviator but after studying flight log and your answer I have a few final questions:
- Where in the log can one see if home point was updated or not?
- Under B log says "Mode changed to P-GPS". What does that mean if it never went into GPS mode?
- Searched in the log for GPS Health, where can I find those numbers (0/5)?

Please be forgiving for these "childish" questions from an old learner.

 

[mfpullenP4]

Pelleplutt… did you ever get an answer for this? I had a simile issue and was wondering too.

 

[Meta4]

Pelleplutt… did you ever get an answer for this? I had a simile issue and was wondering too.

- Where in the log can one see if home point was updated or not?
- Under B log says "Mode changed to P-GPS". What does that mean if it never went into GPS mode?
- Searched in the log for GPS Health, where can I find those numbers (0/5)?

Please be forgiving for these "childish" questions from an old learner.

Sorry Pelleplutt ... I didn't see your additional questions until now.

I looked into the actual data, which you can see by clicking the CSV link under the map in teh Airdata overview page.
It has two columns for GPS number of sats and GPS Level, which is an indication of the flight controller's assessment of GPS data quality
I can't say why it indicates the drone went to P-GPS.
It's a false indication as the GPS health never went above zero.
It has to be either 4 or 5 before the drone will actually go to P-GPS.

 

[pelleplutt]

Thanks Meta4, CSV file has it all, never looked there.

When making this flight I was surrounded by high trees in three directions, probably/certainly not adviseable.

Hope this answer from Meta4 also satisfies mfpullen4. For me this thread can be closed.
I have learned to be more accurate and double check everything before take off.

Thank you!

 

[Meta4]

When making this flight I was surrounded by high trees in three directions, probably/certainly not adviseable.

That explains the problem acquiring satellites.
Heavy tree cover blocks satellite signals.
The less sky available, the less satellites you can receive signals from.