Computation and analysis of aircraft proximities in the NAS using ETMS data

Potential airborne conflicts or near-conflicts (jointly referred to as aircraft proximities) are an important National Airspace System activity indicator by itself and also as a component of the dynamic density metric. Proximity analysis in four dimensions using historical data (specifically, Enhanced Traffic Management System files) presents a number of challenges. If we use actual flight tracks, they have conflict resolution actions by air traffic control already embedded into them. If we use flight-plans-as-filed, the time component of the 4D tracks needs to be constructed correctly. To simply use the filed departure time or the estimated/actual departure time as the start time for such tracks would distort the timing and location of the potential airborne conflicts because of the wide variance of out-to-off times for different airports and times of the day. In this paper, we propose a method that uses a combination of actual and planned tracks resulting in a more realistic timing of potential conflicts. An efficient scanning algorithm for computing 4D proximities is introduced. The results are displayed on a hexagonal grid over the National Airspace System. The method is also compared with the output from fast-time simulations using TAAM (Total Airport & Airspace Modeler), a well-known air traffic simulation model.