PURPOSE: To enable highly accurate measurement of a position by shifting one signal in time by a maximum value of correlation out of signals received at two points while a scalar product of a vector component between the signal and the other signal.

CONSTITUTION: Response signals Sa and Sb of responders A and B are received with two receiving stations 1 and 2 composing a set and processed with a correlator of a processor 5 to shift anyone thereof, for example, a received signal E1 (t) in time by a time giving a maximum value of correlation while a scalar product of a vector component is determined between the signal and the other signal to emphasize the signal Sa with a maximum intensity of a received electric field from among the signals Sa and Sb. When this signal is contained in a basic pulse train in a secondary radar system, the signal Sa is encoded to identify the responder A. Moreover, the signal Sa emphasized is erased from received signals E1 (t) and E2 (t) at the two points thereby allowing sequential identification from the one with a higher intensity of the received electric field to the one with a less intensity thereof.