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 excellentworking 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 knowledgeabout individual objects.*** Sometimes we refer to this function as �track and trace� because that is what we are doing to* eachobject in the model. In Marc Adler�s recent shoplifting scenario, Marc was interestedin trackingand tracing peoplein 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)*andother flying objects (known migratory bird paths, swarms of insects) to our simple model.**
Complex event processing occurs when we are processing*multipleobjects 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 isconsiderable �complex event processing� that goes on �behind the scenes�to provide air traffic controllers and pilotssituational knowledge into the �friendly skies�.** As youmight furtherimagine, 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 andthe 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 optimaldecisions can be made.
This is true, by the way, forour shoplifting example (the impact is different if a pieceof 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 andhelp mefurther refine this ATC model, if he has time.