As the demand for air transportation increases, the capacity of the current U.S. ATM system will eventually be stressed to its limits. New technologies in communication, navigation, and surveillance (CNS), along with new decision-support systems and an evolutionary development of the ATM system architecture, can extend the capacity of the current system for several years. NASA has developed a new method and system, based on Extensible Markup Language (XML), that relates to control of aircraft traffic through specification of trajectory coordinates.
The trajectories are composed of a series of trajectory segments. The process involves analysis and processing information on one or more aircraft flight paths, using four-dimensional coordinates (x, y, z) and a fourth coordinate r that corresponds to a distance estimated along a reference flight path to a nearest reference path location corresponding to a present location of the aircraft. Use of the coordinate r, rather than elapsed time t, avoids coupling of along-track error into aircraft altitude, and reduces effects of errors on an aircraft landing site.
Along-track error, cross-track error, and altitude error are calculated relative to an ideal, conflict-free reference flight path. Elapsed time is monitored and used as an independent variable for computing or measuring along-track, cross-track, and altitude locations and errors. An error tube is numerically constructed around a central axis, such as the conflict-free reference flight path, with an along-track range delta AT, a cross-track range delta CT, and an altitude range delta AL that may vary with the distance r along the reference flight path. Altitude is preferably specified as a function of along-track distance r, rather than as a function of time t. A trajectory specification will be used for communicating trajectory information between an aircraft and one or more ground systems, such as an Airline Operation Center (AOC), for scheduling, maintaining aircraft separation, and other relevant activities.