PURPOSE: To allow highly accurate measurement of position and azimuth of a mobile by providing a timer starting measurement of time with light receiving time signals and non-directional signals received by a plurality of optical sensors and ending measurement of time with a delay signal.

CONSTITUTION: A laser beam transmitter 1 installed on the ground G transmits a laser beam 9 turning at a constant angular speed. When the laser beam 9 transverses an optical sensor 4 in a non-directional signal transmitter 3, a radio signal is transmitted from an antenna 3a. A mobile 2 carries an antenna 5a receiving radio signal, and a plurality of linear optical sensors 6-8 for receiving the laser beam 9 sequentially and outputting information relevant to light receiving time and position. Time to be elapsed after start of light receiving time signal before end of delay time for the sensor 6(signal is outputted with a time lag behind light receiving time of the sensors 7, 8), and time to be elapsed after start of light receiving time signal for the sensors 7, 8, and the receiver 5a, are measured through respective timers. The measurements are employed in the operation of position or azimuth of the mobile 2.