Why gps glitch when activated mavros gps

I have tried mavros GPS on quadrotor. But every time the Mavros GPS is turned on (guided mode), a GPS Glitch notification appears so that the vehicle goes into land mode.

what is the cause? and what is the solution?

Typicylly the problem are too many tall buildings or electromagnetic interference.

Google for “GNSS multipath” for more info

And update to ArduCopter 4.3.3

mavros GPS will work if HDOP is below 0.7