The present invention concerns a localization method for locating a target that is coupled with a locator transponder associated with a permanent identification code permanently assigned to said locator transponder; the localization method comprising: upon reception of a user request for locating the target, transmitting, by a paging system or by a radar-based system, a spread spectrum paging signal carrying the permanent identification code and a temporary identification code temporarily assigned to the locator transponder, wherein said temporary identification code is shorter than said permanent identification code; receiving, by the locator transponder, the spread spectrum paging signal and extracting, by said locator transponder, the temporary identification code carried by said spread spectrum paging signal received; transmitting, by the radar-based system, radar signals towards one or more areas of earth's surface or sky, and receiving, by said radar-based system, echo signals from said one or more areas of the earth's surface or sky; upon reception by the locator transponder of one or more radar signals transmitted by the radar-based system, generating and transmitting, by said locator transponder, a sequence of watermarked radar echo signals in which a spread spectrum watermarking signal is embedded, wherein said spread spectrum watermarking signal carries the temporary identification code extracted.