Disconnected in flight - Mavic 2 Pro gone

[Mossiback]

...sounds like the difference between a GPS "cold start" and "warm start".

I've never heard of a GPS cold and warm start. Thanks for the education.

 

[Mossiback]

Recalibrating the IMU made no difference...

Not to beat a dead horse, but how do you explain the change in homepoint update time before and after the IMU calibration? I was flying at one place with two or three batteries and the homepoint update took much longer before the IMU calibration than after and the calibration was the only change made.

 

[BudWalker]

Perhaps I worded it incorrectly. My MP would show enough satellites to establish the home point but it would take sometimes over a minute to actually do it. After calibrating the IMU it would establish the home point within seconds.

I suspect what you're seeing is due to the HP not being set until navHealth reaches 4 (out of 5). NavHealth is the confidence the FC has in the Lat/Long it's computing and depends on more than just having a GPS solution. It also depends on the gyro, accelerometer and magnetometer data. To tell the truth I don't know exactly what happens during an IMU calibration but it's certainly plausible that a better calibration could shorten the length of time it takes for the FC to like it's Lat/Long solution.

Perhaps a .DAT from a flight where there was a delayed HP acquisition would provide more info.

 

[Meta4]

Not to beat a dead horse, but how do you explain the change in homepoint update time before and after the IMU calibration? I was flying at one place with two or three batteries and the homepoint update took much longer before the IMU calibration than after and the calibration was the only change made.

If you flew and noted a slow GPS acquisition/homepoint recording time, changed batteries and flew again, you would normally expect to see a faster GPS acquisition time anyway without playing with the IMU.
Go to this link and read the section titled Start Times:

How GPS Receivers work - Tutorial Australia

GPS is accurate and handy to use, so much so that we rely on it more and more every day. It's not often we take the time to learn how it works. The idea of GPS refers to a Global Positioning System; a collection of satellites in orbit above the Earth that transmit location data down to our...

core-electronics.com.au

Or this:

Time to first fix - Wikipedia

en.wikipedia.org

 

[Mossiback]

If you flew and noted a slow GPS acquisition/homepoint recording time, changed batteries and flew again, you would normally expect to see a faster GPS acquisition time anyway without playing with the IMU...

That is also what I would expect, but not what was happening. After the first flight there was the same delay in setting the homepoint as in the first flight. After calibrating the IMU the delay was much shorter. I am not going to pretend that I know how things work but that is my observation.

I do appreciate your comments and suggestions.

 

[ea4eob]

Recalibrating the IMU made no difference.
It couldn't have because the GPS receiver does not get any other data from the drone.
It's completely independent.
What you describe is completely normal and sounds like the difference between a GPS "cold start" and "warm start".

The problem is next day lost GPS sats in the air at same time than disconnected from RC... when I restar the RC reconnect and can read landing... but not RTH but at the sea because the MV have not any GPS valid position...
Is very strange...

 

[Thomas B]

The problem is next day lost GPS sats in the air at same time than disconnected from RC... when I restar the RC reconnect and can read landing... but not RTH but at the sea because the MV have not any GPS valid position...
Is very strange...

The drone can be set to RTH or hover/land on loss of signal. Check your settings to see if it actually followed directions you gave.

 

[Meta4]

The drone can be set to RTH or hover/land on loss of signal. Check your settings to see if it actually followed directions you gave.

But without GPS, the drone cannot RTH.

The problem is next day lost GPS sats in the air at same time than disconnected from RC... when I restar the RC reconnect and can read landing... but not RTH but at the sea because the MV have not any GPS valid position...
Is very strange...

It should have been possible to cancel the autolanding by flicking the flight mode switch out of P-GPS and back.
The unusual thing is losing GPS out in the open.

 

[Saigondroner]

The plot thickens....

Very interested to see in the MCDatFlightRecords that there are no . DAT files from the Mavic 2 Pro....only from my previous Mavic Pro up to March this year. I did find a couple more .txt files from today in the Sync folder, but no .DAT files, uploading them as well in case they help.

Sorry for my ignorance here....I thought that I had been lucky over the last few years because I had escaped so many of the problems that I read about on the forums, so had never had to the need to investigate like this before. That was until today....

thanks again !

I hope you locate it. I now check all my logs, it's good to know why a flight went right also.