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: a) upon reception of a user request for locating the target, transmitting, by a radio communications 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; b) receiving, by the locator transponder, the spread spectrum paging signal and extracting, by said locator transponder, the temporary identification code carried by the received spread spectrum paging signal; c) transmitting, by a 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; d) 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; and e) carrying out, by the radar-based system, localization operations that include - detecting, in the received echo signals, the sequence of watermarked radar echo signals transmitted by the locator transponder, - extracting the temporary identification code carried by the spread spectrum watermarking signal embedded in the detected sequence of watermarked radar echo signals, and - determining a location of the locator transponder on the basis of the detected sequence of watermarked radar echo signals; characterized by further comprising: f) transmitting, by the radio communications system, one or more frequency-synchronization-aid signals; g) receiving, by the locator transponder, the frequency-synchronization-aid signal(s) and estimating, by said locator transponder, based on the received frequency-synchronization-aid signal(s), a frequency drift affecting a reference frequency provided by a local oscillator of said locator transponder; wherein the locator transponder transmits the sequence of watermarked radar echo signals by using a transmission carrier frequency obtained based on the reference frequency provided by the local oscillator and on the estimated frequency drift. a) upon reception of a user request for locating the target, transmitting, by a radio communications 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; b) receiving, by the locator transponder, the spread spectrum paging signal and extracting, by said locator transponder, the temporary identification code carried by the received spread spectrum paging signal; c) transmitting, by a 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; d) 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; and e) carrying out, by the radar-based system, localization operations that include - detecting, in the received echo signals, the sequence of watermarked radar echo signals transmitted by the locator transponder, - extracting the temporary identification code carried by the spread spectrum watermarking signal embedded in the detected sequence of watermarked radar echo signals, and - determining a location of the locator transponder on the basis of the detected sequence of watermarked radar echo signals; - detecting, in the received echo signals, the sequence of watermarked radar echo signals transmitted by the locator transponder, - extracting the temporary identification code carried by the spread spectrum watermarking signal embedded in the detected sequence of watermarked radar echo signals, and - determining a location of the locator transponder on the basis of the detected sequence of watermarked radar echo signals; f) transmitting, by the radio communications system, one or more frequency-synchronization-aid signals; g) receiving, by the locator transponder, the frequency-synchronization-aid signal(s) and estimating, by said locator transponder, based on the received frequency-synchronization-aid signal(s), a frequency drift affecting a reference frequency provided by a local oscillator of said locator transponder;