The Compass and the GPS question!

[wings]

Would like to have someone with the knowledge explain to me the way the compass and GPS work together. Why is it that if the compass gets out of whack, even though the GPS is still giving good signals, the drone may take off. If something causes the compass to become "inaccurate" does that in turn cause the GPS signal to become "inaccurate" and the drone will take off? The way this all works still seems to be a mystery, at least to me.

 

[CraigCam]

Would like to have someone with the knowledge explain to me the way the compass and GPS work together. Why is it that if the compass gets out of whack, even though the GPS is still giving good signals, the drone may take off. If something causes the compass to become "inaccurate" does that in turn cause the GPS signal to become "inaccurate" and the drone will take off? The way this all works still seems to be a mystery, at least to me.

The GPS knows spatial placement but not heading. The compass knows what north is so it can triangulate the GPS information and keep you flying straight per your stick commands. They work together calculating your flight parameters in the flight control processor to send proper signals to motors and radio. A fly away is when this information is scrambled and the drone thinks it should be elsewhere. Turning off GPS disables the autonomous control and it’s all on you to hold position and heading. I prefer no GPS for close video work as the motion is smoother but hover is impossible. It’s an issue for us that the GPS switch is buried in the sub menu for easy pilot access.

 

[wings]

The GPS knows spatial placement but not heading. The compass knows what north is so it can triangulate the GPS information and keep you flying straight per your stick commands. They work together calculating your flight parameters in the flight control processor to send proper signals to motors and radio. A fly away is when this information is scrambled and the drone thinks it should be elsewhere. Turning off GPS disables the autonomous control and it’s all on you to hold position and heading. I prefer no GPS for close video work as the motion is smoother but hover is impossible. It’s an issue for us that the GPS switch is buried in the sub menu for easy pilot access.

Craig: That is an excellent explanation that I can finally understand. I also wish they could use that Aux button that is doing nothing, to activate or deactivate the GPS. I have read where the Plus model is even more difficult to get to the GPS and turn off. Going back to the Compass for a moment I have read where the Compass module in the H is a weak link. As important as it is you would think that Yuneec would have installed a more robust unit.

 

[CraigCam]

Yuneec has had this problem since the Blade 350. Those compass modules would just quit. They are probably easily magnetized. The top mount and heavy copper shielding is good for GPS antenna and compass safety on the H and part of the fix. Their calibration procedure is doing both axis together with the flipping and rotating and I think that’s suspect. My X Star calibrates so much easier with the two spin around technique like DJI. I’ve found facing North at start and always keep the H level as possible during calibration helps. I roll slow enough that I often get a successful point logged in one roll around. If it takes three flips, I consider that suspect and will do it again. I also empty my pockets of everything and leave the ST back at set up point and calibrate where it’s most level and clear of objects. I have experienced a sketchy unit becoming smarter and more reliable by calibrating everyday until it stopped giving warnings. I also discovered the status light can throw errors and sometimes that’s the problem, not the compass. There are sensitivity adjustments on some of the electronics but we don’t have schematics to know their purpose. If compass warnings use any voltage feedback from the light (as it should since it’s a diode) I can get why that’s related. Buying a new status LED board cleaned up my funky always give warnings ship and now that one went from sketchy PIA flyer to super reliable fast GPS locking drone.

 

[PatR]

My feelings have a compass error an indicator of a failure within the flight control system, and not an failure indication of the compass or GPS components. The failure message would be but a triggered sequential warning response, not the actual issue, where the true issue induces further system failures such as those with compass and GPS.

 

[Dustoff]

Craig: That is an excellent explanation that I can finally understand. I also wish they could use that Aux button that is doing nothing, to activate or deactivate the GPS. I have read where the Plus model is even more difficult to get to the GPS and turn off. Going back to the Compass for a moment I have read where the Compass module in the H is a weak link. As important as it is you would think that Yuneec would have installed a more robust unit.

Would be nice to have a hardware switch or button to turn on and off gps

 

[PatR]

The H-480 does have a software switch.

 

[rdonson]

The H-480 does have a software switch.

...and when the adrenaline is flowing because of a flyaway its not easy to execute on that software switch before your drone is stuck in a tree or off on an trip to Timbuktu

 

[PatR]

I didn't say it was ideal