Algorithm 1: Operational process of the switching algorithm
1:	Initialize the system vehicle speed, attitude and position
2:	for System loop
3:	The system collects relevant experimental data through the data port
4:	Update the system attitude quaternion
5:	if The system is located in the ground environment
6:	The system updates the current position and speed by GNSS
7:	if The system detects the switching flag signal
8:	The system shields the GNSS satellite signal
9:	end if
10:	else The system is located in underground garage environment
11:	The system updates the current position by gyroscope and vehicle speed
12:	if The system is started in underground garage
	The magnetometer initializes heading of the gyroscope
13:	end if
14:	end if
15:	end for