Lost all control and crashed

Well guys I've got to admit I'm a little lost with the last few posts but I'm finding it a very interesting read.
Update I'm still waiting for the quad to be picked up and sent for inspection to see if I have a warrant claim ,what would be your thoughts?
 
I will PM you.

OK - I think I know what is leading to the different opinions on the viability of this approach - we really are talking about two quite different, although superficially similar methods, which goes back to my comment about flight stability control vs. navigational control. Those are not, necessarily, the same thing and it’s worth looking again at exactly how they work.

Looking at the DJI IMU sensor packages, the accelerometers and rate gyros report at 200 samples/second, and the magnetometers at 50 samples/second. The GPS units report at 5 samples/second. There is sensor overlap here in terms of measured and derived quantities. The accelerometers are reporting the second time derivative of position, while the GPS units are reporting both the first time derivative of position (velocity) and position itself. The rate gyros are reporting the first time derivative of yaw, while the magnetometers are reporting yaw itself.

The way this works, in normal P-GPS mode, is that when the IMU initializes it determines a starting absolute position from GPS data and starting yaw from the magnetometers. After that, the primary sources of updates to the position and yaw are derived from integrating (with respect to time) the high-frequency accelerometer and yaw data, not from the lower frequency GPS and magnetometer absolute data with those only being used as weighted adjustment data to correct for bias and drift in the fast sensors. The reason for this, of course, is that the GPS data, for example, have neither the spatial nor temporal resolution necessary for the high-frequency precise control of the motors needed for flight stability. And if you take a look at the lat/long data in the DAT file you will notice that they really are being updated at 200 Hz, not the 5 Hz rate of the GPS data stream, and that the lat/long reported by the IMU are not identical to the lat/long GPS data.

Considering next the situation with untrustworthy magnetometer data, what we have lost is an absolute yaw value. That means that neither absolute yaw nor position can be updated at the required 200 Hz rate. The yaw for obvious reasons, and position because the high-frequency displacement data derived from the accelerometers are still present, but only known in the aircraft frame of reference - they cannot be transformed into the earth frame of reference (lat/long) without knowing the yaw value. That is the primary reason why in ATTI mode the FC cannot avoid yaw drift and does not attempt to hold position, even though it does know where it is from the GPS data - those are not fast or accurate enough for flight control. That is also, I strongly suspect, the basis for the observations that GPS cannot replace the magnetometer data - it cannot for that flight control purpose - which would require much more expensive and higher-resolution GPS equipment.

However, that would not prevent the method that I described earlier where the flight stability is under ATTI but with a parallel, low-frequency feedback loop used to drive the aircraft in a particular direction (e.g. towards the home point). That is a much lower tech solution that does not require any change in equipment or much processing power, and I've no idea whether or not it has even been considered in that context.
 
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.....The yaw for obvious reasons, and position because the high-frequency displacement data derived from the accelerometers are still present, but only known in the aircraft frame of reference - they cannot be transformed into the earth frame of reference (lat/long) without knowing the yaw value. ........
This. (I added the emphasis)

This is the reason that gpsHealth will drop to 1 or 0 in situations where, if anything, a compass error could happen. The FC decides that Yaw can't be trusted and, therefore, the GPS computation can't be trusted. I've wondered why the DJI response to this type of gpsHealth problem is to calibrate the compass.
 
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Sounds like what happen to me almost word for word only difference mined landed in a muddy quicksand pit right in the middle my luck.
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that god for the boat
 

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