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Trajectory Specification For High-Capacity Air Traffic Control

Trajectory Specification For High-Capacity Air Traffic Control. Russ Paielli NASA Ames Research Center AIAA ATIO-06 Conference Wichita, KS, Sept 27, 2006. [paper available at http://RussP.us/publist.htm]. Outline. Motivation Trajectory prediction Trajectory specification

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Trajectory Specification For High-Capacity Air Traffic Control

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  1. Trajectory Specification For High-Capacity Air Traffic Control Russ Paielli NASA Ames Research Center AIAA ATIO-06 Conference Wichita, KS, Sept 27, 2006 [paper available at http://RussP.us/publist.htm]

  2. Outline • Motivation • Trajectory prediction • Trajectory specification • Error tolerances and bounding space • Horizontal and vertical specifications • Polynomial approximation • XML • Concluding remarks

  3. Motivation • Demand for domestic air travel expected to double or triple within ~20 years • Airspace capacity currently limited by controller workload (~15 aircraft/sector max) • Automated separation assurance can increase airspace capacity • 4D trajectories can facilitate automated separation assurance • No standard currently exists for specifying and communicating continuous 4D trajectories with error tolerances

  4. Trajectory Prediction

  5. Trajectory Specification

  6. 4D Trajectory Specification • Not just a series of 4D points! • 3D fixed tube with position along tube as fourth dimension • Groundtrack composed of straight (great circle) segments and constant-radius turns (2D) • Altitude as function of along-track distance (third dimension) • Along-track position as function of time (fourth dimension) • Error tolerances determine bounding space around reference trajectory

  7. Trajectory Error Tolerances • Explicit along-track/cross-track/vertical tolerances • Conformance required with high reliability • Can vary with traffic situation • Limited by navigation capability of aircraft • Looser tolerances in light traffic • Determine a precisely specified bounding space for each aircraft at each point in time • Useful for automated separation assurance • Disabled vertical and/or along-track bounds reduce dimension of specified trajectory • could be useful for early implementation

  8. Advantages of Explicit Bounding Space • Enhanced fault tolerance • Conflict-free trajectories can be guaranteed for given time horizon even if ground systems and/or datalink fail • Maximize airspace capacity • Particularly useful in weather-constrained areas • Comparable to painting lane lines on roads

  9. Capacity EnhancementIn Weather-constrained Areas

  10. Misunderstandings to AvoidAbout Trajectory Specification • Does not imply centralized “control” • But facilitates centralized coordination • Can be used to downlink trajectory requests or uplink trajectory assignments • Does not mandate “precise” tracking of 4D reference trajectory • Precisely specifies bounds on aircraft position at any point in time • Bounds can be large when appropriate

  11. Horizontal Trajectory Specification • Two segment types • straight (greatcircle) • turn (circular arc) • Each segment defines own coordinate system • Along-track/cross-track tolerances define bounding space • Along-track updates compensate for wind modeling errors

  12. Vertical Trajectory Specification

  13. Problem With Altitude As Function Of Time

  14. Leveloff Transition Tolerance

  15. Why XML? • Text format less error-prone and more flexible than binary format • Directly readable by engineers/developers • Flexible selection and ordering of data fields • Replacing binary formats in many domains • e.g., B2B, SVG, OpenDocument, MS Office • Independent of computer platform and programming language • Versatile, popular, standardized

  16. XML Sample <segment number="1" vtype="climb" htype="straight" stype="constCAS"> <time start="0:08:42" duration="7:42"/> <begin lat="xxx.xxxx“ lon="xxx.xxxx"/> <end lat="xxx.xxxx“ lon="xxx.xxxx"/> <along coeffs="xxx.xxx xxx.xxx" CAS="280" length="27.815"/> <alt coeffs="126.8 21.609 4.1417e-3" thrust="90" end="270" /> </segment>

  17. Concluding Remarks • 4D trajectory specification • 3D tube with position along tube as fourth dimension • Error tolerances define bounding space at each point in time • Facilitates automated separation assurance and resulting increased airspace capacity • XML is a strong candidate for the job • Versatile, popular, standardized • Lead time for establishing and implementing standards is very long -- no time to waste!

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