Passive Surveillance System
The Czech industry has a long tradition and to a great extent a unique position in the area of the passive surveillance systems (PSS). It was in former Czechoslovakia in 1958, when a method of passive location of a signal source was discovered. The method is based on evaluation of time differences of incoming signals to three receivers each far off dozens of kilometres.
The immediate location of the source is at the intersect of hyperbolic curves calculated from time differences of incoming signals. The method was therefore named „time-measure-hyperbolic“ , while at present the method is known as TDOA (Time Difference of Arrival Location).
The newly discovered method has been developed into operational use and a new category of radio-location technology was introduced - the passive surveillance systems.
The system can detect radio and radar signals emitted from a variety of air, land or water-surface sources. It sets their grid lines in two or three dimensions, analyses received signals and automatically (or by an operator) identifies type of the target, or its functional mode.
Compiled from texts written by Michal Zdobinský, Military Information and Service Agency, Prague