The Effect of M-Code Multipath on Ephemeris Generation

R.B. Harris, E.G. Lightsey

Abstract:	The accuracy of the ephemerides produced by the National Geospatial-Intelligence Agency (NGA) and the GPS Operational Control Segment (OCS) is tied to the accuracy of the range measurements produced by their almost identical measurement conditioning processes, which feature carrier phase smoothing of the pseudorange. While smoothing greatly reduces the impact of noise, systematic errors due to multipath can in some cases remain. In others, smoothing appears to remove the impact of multipath. Both cases be attributed to properties of Binary Phase Shift Key (BPSK) modulation and receiver design parameters. In the future, those networks may substitute the Binary Offset Carrier (BOC) modulated M-Code for the BPSK modulated precise code currently tracked by their receivers. The signature of multipath will still persist through the smoothing process, but that signature will change. The maximum error associated with pseudorange multipath error will decrease, however there will be more conditions for multipath error to occur. Similarly, the opportunities for carrier phase multipath error will increase.
Published in:	Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009) September 22 - 25, 2009 Savannah International Convention Center Savannah, GA
Pages:	155 - 166
Cite this article:	Harris, R.B., Lightsey, E.G., "The Effect of M-Code Multipath on Ephemeris Generation," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 155-166.
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