Trajectory Specification For High-Capacity Air Traffic Control


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  • Trajectory Specification For High-Capacity Air Traffic Control

    1. 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]
    2. 2. Outline <ul><li>Motivation </li></ul><ul><li>Trajectory prediction </li></ul><ul><li>Trajectory specification </li></ul><ul><ul><li>Error tolerances and bounding space </li></ul></ul><ul><ul><li>Horizontal and vertical specifications </li></ul></ul><ul><ul><li>Polynomial approximation </li></ul></ul><ul><li>XML </li></ul><ul><li>Concluding remarks </li></ul>
    3. 3. Motivation <ul><li>Demand for domestic air travel expected to double or triple within ~20 years </li></ul><ul><li>Airspace capacity currently limited by controller workload (~15 aircraft/sector max) </li></ul><ul><li>Automated separation assurance can increase airspace capacity </li></ul><ul><li>4D trajectories can facilitate automated separation assurance </li></ul><ul><li>No standard currently exists for specifying and communicating continuous 4D trajectories with error tolerances </li></ul>
    4. 4. Trajectory Prediction
    5. 5. Trajectory Specification
    6. 6. 4D Trajectory Specification <ul><li>Not just a series of 4D points! </li></ul><ul><li>3D fixed tube with position along tube as fourth dimension </li></ul><ul><li>Groundtrack composed of straight (great circle) segments and constant-radius turns (2D) </li></ul><ul><li>Altitude as function of along-track distance (third dimension) </li></ul><ul><li>Along-track position as function of time (fourth dimension) </li></ul><ul><li>Error tolerances determine bounding space around reference trajectory </li></ul>
    7. 7. Trajectory Error Tolerances <ul><li>Explicit along-track/cross-track/vertical tolerances </li></ul><ul><li>Conformance required with high reliability </li></ul><ul><li>Can vary with traffic situation </li></ul><ul><ul><li>Limited by navigation capability of aircraft </li></ul></ul><ul><ul><li>Looser tolerances in light traffic </li></ul></ul><ul><li>Determine a precisely specified bounding space for each aircraft at each point in time </li></ul><ul><ul><li>Useful for automated separation assurance </li></ul></ul><ul><li>Disabled vertical and/or along-track bounds reduce dimension of specified trajectory </li></ul><ul><ul><li>could be useful for early implementation </li></ul></ul>
    8. 8. Advantages of Explicit Bounding Space <ul><li>Enhanced fault tolerance </li></ul><ul><ul><li>Conflict-free trajectories can be guaranteed for given time horizon even if ground systems and/or datalink fail </li></ul></ul><ul><li>Maximize airspace capacity </li></ul><ul><ul><li>Particularly useful in weather-constrained areas </li></ul></ul><ul><ul><li>Comparable to painting lane lines on roads </li></ul></ul>
    9. 9. Capacity Enhancement In Weather-constrained Areas
    10. 10. Misunderstandings to Avoid About Trajectory Specification <ul><li>Does not imply centralized “control” </li></ul><ul><ul><li>But facilitates centralized coordination </li></ul></ul><ul><ul><li>Can be used to downlink trajectory requests or uplink trajectory assignments </li></ul></ul><ul><li>Does not mandate “precise” tracking of 4D reference trajectory </li></ul><ul><ul><li>Precisely specifies bounds on aircraft position at any point in time </li></ul></ul><ul><ul><li>Bounds can be large when appropriate </li></ul></ul>
    11. 11. Horizontal Trajectory Specification <ul><li>Two segment types </li></ul><ul><ul><li>straight (greatcircle) </li></ul></ul><ul><ul><li>turn (circular arc) </li></ul></ul><ul><li>Each segment defines own coordinate system </li></ul><ul><li>Along-track/cross-track tolerances define bounding space </li></ul><ul><li>Along-track updates compensate for wind modeling errors </li></ul>
    12. 12. Vertical Trajectory Specification
    13. 13. Problem With Altitude As Function Of Time
    14. 14. Leveloff Transition Tolerance
    15. 17. Why XML? <ul><li>Text format less error-prone and more flexible than binary format </li></ul><ul><ul><li>Directly readable by engineers/developers </li></ul></ul><ul><ul><li>Flexible selection and ordering of data fields </li></ul></ul><ul><li>Replacing binary formats in many domains </li></ul><ul><ul><li>e.g., B2B, SVG, OpenDocument, MS Office </li></ul></ul><ul><li>Independent of computer platform and programming language </li></ul><ul><li>Versatile, popular, standardized </li></ul>
    16. 18. XML Sample <segment number=&quot;1&quot; vtype=&quot;climb&quot; htype=&quot;straight&quot; stype=&quot;constCAS&quot;> <time start=&quot;0:08:42&quot; duration=&quot;7:42&quot;/> <begin lat=&quot;xxx.xxxx“ lon=&quot;xxx.xxxx&quot;/> <end lat=&quot;xxx.xxxx“ lon=&quot;xxx.xxxx&quot;/> <along coeffs=&quot;; CAS=&quot;280&quot; length=&quot;27.815&quot;/> <alt coeffs=&quot;126.8 21.609 4.1417e-3&quot; thrust=&quot;90&quot; end=&quot;270&quot; /> </segment>
    17. 19. Concluding Remarks <ul><li>4D trajectory specification </li></ul><ul><ul><li>3D tube with position along tube as fourth dimension </li></ul></ul><ul><ul><li>Error tolerances define bounding space at each point in time </li></ul></ul><ul><ul><li>Facilitates automated separation assurance and resulting increased airspace capacity </li></ul></ul><ul><li>XML is a strong candidate for the job </li></ul><ul><ul><li>Versatile, popular, standardized </li></ul></ul><ul><li>Lead time for establishing and implementing standards is very long -- no time to waste! </li></ul>