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Surveillance Systems

The purpose of a surveillance system is to detect and track Objects Of Interest (OOI) that are present within a spatial volume covered by a sensing device. Surveillance systems can be classified into four types:

  • Cooperative and synchronized
  • Cooperative and unsynchronized
  • Un-cooperative and active
  • Un-cooperative and passive

In cooperative systems, the OOI are equipped with a transponder device that voluntarily “cooperates” with  the sensor. The sensor continuously probes the surveillance volume by transmitting an interrogation signal that is recognized by the OOI transponders. When a transponder detects an interrogation, it  transmits a response signal back to the interrogator. The response may contain identification and other information of interest to the interrogator. Air traffic control radar systems are examples of cooperative, synchronized surveillance systems.


In a cooperative and unsynchronized surveillance system, the sensor doesn’t actively probe the surveillance volume. It passively waits for signal emissions from beacon-equipped OOI. Cooperative and unsynchronized surveillance systems are less costly than cooperative and synchronized systems, but because the OOI beacon emissions aren’t synchronized by an interrogator, their signals can garble each other and make it difficult for the sensor detector to keep them separated.


In uncooperative surveillance systems, the OOI aren’t equipped with any man made devices designated to work in conjunction with a remotely located sensor. The OOI are usually trying to evade detection and/or the sensor is trying to detect the OOI without letting the OOI know that they are under surveillance.

In an active, uncooperative surveillance system, the sensor’s radiated signal is specially designed to reflect off of an OOI. The time of detection of the reflected signal can be used to determine the position and speed of an OOI. Military radar and sonar equipment are good examples of uncooperative surveillance systems.


In a passive, uncooperative surveillance system, the sensor is designed to detect some type of energy signal (e.g. heat, radioactivity, sound) that is naturally emitted or reflected (e.g. light) by an OOI. Since there is no man made transmitter device in the system design, the detection range, and hence coverage volume, is much smaller than any of the other types of surveillance systems.


The dorky classification system presented in this blarticle is by no means formal, or official, or standardized. I just made it up out of the blue, so don’t believe a word that I said.

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