Tim Bass
09-08-2008 06:27 AM
Today I will discuss*a general approach to model air traffic control (ATC)*using our
CEP/EP reference architecture which is an application of the mature
JDL multisensor data fusion model.
ATC is an excellent*working example of complex event processing.** Radar and GPS provide the basic sensory information to accurately track and trace the position of each aircraft in the area of responsibility (AOR) of a particular control tower/zone.**** Naturally,* sensory information is preprocessed and formatted in such a way that the data can be processed upstream by multiple real-time applications.
Before we look at complex ATC scenarios, such as “potential collision” or “aircraft off approach vector” we must trace and trace individual objects, aircraft-objects,*accurately with very high confidence.*** In addition to tracking*aircraft-objects, there is a database of information about the aircraft (ideally), such as make, model, age, range, passengers and other properties about the aircraft-object.***** In addition, there is a state-model for each aircraft, for example the aircraft might be “on the ground”, “approaching the runway”, “cleared for takeoff”, “crusing altitude”, “approaching runway”, “final desent” etc.**
Tracking and tracing individual aircraft is what is generally referred to as “object refinement” in our CEP/EP reference architecture.** The reason we call this function “object refinement” is that system engineers are focused on optimizing the situational knowledge*about individual objects.**** Sometimes we refer to this function as “track and trace” because that is what we are doing to* each*object in the model.* In Marc Adler’s recent
shoplifting scenario, Marc was interested*in tracking*and tracing people*in a store using imaging processing techniques to estimate their behavioral patterns.* In the same way, before we can process for scenarios such as “potential shoplifter” or “suspicious criminal gang activity” we must be able to accurately process (track and trace)*individual object, such as people or merchandise.
Back to aircraft and ATC, the “complex event processing” begins when we are looking about object-object relationships, in this model, aircraft-to-aircraft, but this is an overly simplistic model, as we have not yet added (to our model)*ground features (towers, buildings, power lines), weather (storm cells,*wind)*and*other flying objects (known migratory bird paths, swarms of insects) to our simple model.**
Complex event processing occurs when we are processing*multiple*objects in our model looking for threats in real-time.**** Practically speaking, all ATC applications are CEP applications.* This means that vendors and integrators who build ATC applications are also CEP vendors.***
Editorial Note: CEP/EP has been around for a long time and was not recently invented in the past decade as some “inventors”*would like for us to believe.*
As you can imagine, there is*considerable “complex event processing” that goes on “behind the scenes”*to provide air traffic controllers and pilots*situational knowledge into the “friendly skies”.** As you*might further*imagine, the situation is more complex when the skies are “not so friendly”, for example, in air combat situations.***
Processing myriad objects is not the end of the processing “chain”.* For example, decisions are being made constantly about potential damage, alternative airports, and more.*** In our reference model, we refer to this, generally speaking, as “impact assessment” because we must take an estimated detected complex event, for example “aircraft collision,” and estimate potential damage based on numerous factors such as, the amount of jet fuel in the aircrafts and*the location of the aircrafts (over a large city or rural area, near a hospital and emergency services).** Regardless of the scenario, an impact assessment is normally required before optimal*decisions can be made.
This is true, by the way, for*our shoplifting example (the impact is different if a piece*of gum is stolen versus a $1,000,000 diamond necklace or weapons-grade nuclear material) and other scenarios and models.* Static data (information about objects) is required for accurate decision processing.**
Impact assessment is not the end of the “knowledge chain”.*** Decisions are constantly being made that effect resources.* For example, suggestion an alternative route for an aircraft is a resource management decision.*** Turning on and off radar or switching to alternative tracking devices is a resource management function.* In our CEP/EP reference model (based on the JDL data fusion model), we call this “resource management”.** This function includes contacting emergency services and directing them to a potential crash location or sending out a message to instruct all aircraft to stay off a certain radio frequency.* Resource management is critical.
Our simple ATC model today is by no means complete, it just scratches the surface.* In fact, I have a very close friend who is an former Marine fighter pilot and currently a senior captain for
American Airlines.** I will ask my friend to read this post and*help me*further refine this ATC model, if he has time.
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