Flight Test Data Validation of Dual-Frequency GPS Measurement Error Characteristics

H. Tang, T. Walter, J. Blanch, P. Enge, F-C Chan

Abstract:	With the launch of the GPS-IIF satellites, the new civil navigation signals at L5 (1176.45 MHz) will become available to the GNSS community. One of the most significant benefits introduced by this new signal is that the dual-frequency measurement combination of L5 and the existing L1 C/A signals will eliminate the largest GPS measurement error - the ionosphere delay affecting the L1-only signal. The ionosphere delay will be removed by forming an Iono-free GPS code measurement combination with the dual-frequency signal. Thus, the performances of many GNSS navigation applications, such as the accuracy and integrity metrics in civil aviation, will be dramatically improved. The dual-frequency code measurement combination process suppresses the ionosphere delay; however, it is a double-edged sword, as the combination also increases the contributions of multi-path and receiver noise errors on the GPS measurements. Therefore, carrier smoothing is applied to alleviate the negative impact of these errors. In this paper, the effects of these errors are investigated using the flight test GPS measurement data obtained from FAA flight trials conducted at Memphis International Airport. This data uses the currently available dual frequency data based upon L1 C/A and L2 P(Y) semicodeless signals (since the L5 signal is not available yet, the L2 signal is used as a substitute). This paper also analyzes the effectiveness of the carrier smoothing process for airborne GPS code measurements, in mitigating the increased noise due to the Iono-free measurement combination. The resulting ranging signal qualities of the dual frequency measurements are compared against the qualities of the WAAS-corrected L1-only measurements.
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:	1637 - 1644
Cite this article:	Tang, H., Walter, T., Blanch, J., Enge, P., Chan, F-C, "Flight Test Data Validation of Dual-Frequency GPS Measurement Error Characteristics," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 1637-1644.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In