Ranging/timing off of the NDGPS signal: Potential performance

Document Type

Conference Proceeding

Date of Original Version



Position, Navigation, and Timing (PNT) have become a mainstay of everyday life in the United States; many useful applications have become possible through the Global Positioning Service (GPS). Unfortunately, it has long been known that the GPS is vulnerable and so the development of alternative "backup" PNT systems are recommended. A wide variety of technological solutions to PNT are possible; in the radio frequency (RF) domain we have the so-called "signals of opportunity" systems. This phrase refers to the availability of RF signals whose primary purpose is not PNT, but that could still be used in a PNT receiver. As an RF communications signal with detailed time/frequency domain characteristics, the Nationwide Differential GPS (NDGPS) has the potential to serve as a signal of opportunity ranging signal. Prior published work has examined the performance of the NDGPS system; however, these efforts have focused on the data communications capability (often through coverage diagrams assessing availability) and the resulting navigation accuracy of the corrected GPS signals (often through evaluation of the spatial decorrelation of the corrections), not the use of the signal as a ranging source. At ION GNSS 2007 these authors considered combining pseudoranges from both Loran and the NDGPS system. In unpublished work, we considered the possibility of a stand-alone NDGPS positioning system. The results of this last study, unfortunately, indicated that the NDGPS system is too sparse to provide sufficiently accurate pseudoranges for stand-alone precise 2-D positioning. Our view, however, is that NDGPS has great potential in providing precise time to a timing user or providing an additional range measurement as an integrity check to a GPS positioning user; both of these require only one accurate pseudorange. Toward this end, this paper contains a theoretical assessment of the ranging performance of a single NDGPS signal.

Publication Title

Institute of Navigation International Technical Meeting 2012, ITM 2012



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