A Preliminary Study of LORAN-C Additional Secondary Factor (ASF) Variations

摘要

Currently, there is considerable interest in the LORAN community in the recognition ofrnLORAN-C as “the” backup navigation system for the global positioning system (GPS). A key tornthis recognition is the demonstration to aviation navigation that LORAN-C can achieve thernaccuracy, availability, integrity, and continuity to support non-precision approaches (RNP 0.3).rnTo do so, it is required that we better understand the variations in the LORAN positioin “fix” duernto the changing characteristics of the signal propagation path (so called additional secondaryrnfactors or ASFs). The U.S. Coast Guard Academy, under contract to the Federal AviationrnAdministration (FAA), is attempting to understand and characterize these variations for “all-inview”rnreceivers using time-of-arrival (TOA) data. This paper reports on some recent results inrnthis arena.