A tracking system (100) includes a first device (120) and a second device (140). The first device includes plural ultrasonic sources (121) and an inertial measurement unit (122) configured to detect inertial data. The second device includes at least one ultrasonic receiver (141) and a processor (143). The processor is configured to receive the inertial data, estimate an orientation of the first device according to the received inertial data, determine a first ultrasonic transmitter from the ultrasonic transmitters according to the orientation of the first device and a location of the first device, and send an enablement command about the first ultrasonic transmitter to the first device. The enabled transmitter of the ultrasonic transmitters sends ultrasounds according to the enablement command, the at least one ultrasonic receiver is configured to receive the ultrasounds from the first ultrasonic transmitter, and the processor determines the location of the first device according to the received ultrasounds.