FAA Admits Consideration of Curvature to Earth Produces Navigational Error

VALIDATION OF THE AUTOMATIC-FLIGHT-INSPECTION INSTRUMENT-LANDING-SYSTEM BEST FIT STRAIGHT LINE APPLICATION by David A. Quinet, Avionics Engineering Center School of Electrical Engineering and Computer Science Ohio University:

“A review of the AFIS software indicated that this initial processing took into account earth curvature. Further analysis indicated that this error is minor in computing RDH/ARDH. In fact, at four miles (the most sensitive location for the RDH calculation) the difference in altitude for earth curvature versus a flat earth is 14.10 feet. This introduces an error in the RDH calculation of 1.78 feet. In the Ohio University implementation, all values are converted to East-North-Up coordinates in a locally-level plane referenced to the runway threshold.” (Pg. 3)

https://www.faa.gov/air_traffic/flight_info/avn/flightinspection/onlineinformation/pdf/07-10BFSL_Final.pdf

See also ASSESSING THE VALIDITY OF USING ACTUAL NAVIGATION PERFORMANCE (ANP) INFORMATION FOR SUPPORTING DESIGNATED FLIGHT INSPECTION OPERATIONS by Michael F. DiBenedetto, Ph.D., Senior Research Program Engineer Avionics Engineering Center School of Electrical Engineering and Computer Science Ohio University , Appendix pg. 32-36

https://www.faa.gov/air_traffic/flight_info/avn/flightinspection/onlineinformation/pdf/TM_08-12_AVN_ANP_Final_Report.pdf

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