Abstract: A method for measuring a frequency f=&ohgr;/2&pgr; of a sinusoidal signal V(t)=Asin(&ohgr;t+&agr;) with an essentially constant amplitude A. Measured values are registered in the form of the instantaneous level of the signal V(t), V(t−h) and V(t−2h)at three points of time separated by a predetermined measuring period h, which corresponds to a measurement frequency fs=1/h.

Abstract: The invention relates to a radar station placed on the surface of the earth, and to a radar system comprising at least two such radar stations. The signal-processing equipment of the radar stations is adapted, at each point of time, to calculate probabilities of target positions and radial target velocity in relation to each individual radar station, based on the signals emitted and received by this station. These calculated values are associated over time, giving cumulative probability measures for target positions and radial velocities in relation to each individual radar station. By providing a system of at least two radar stations, it is possible to calculate the position of a target by associating target positions, such as they are perceived by the different radar stations, with each other by an association of characteristic movements of the target. This is done without having to synchronize the stations.