Statistical Analysis of Military and Civilian Navigation Error Data Services

Ted Driver

Abstract:	Objective: Determine a statistical difference in navigation accuracy, if any exists, between data provided by a Military Error Data Service and Civilian Error Data Service. Methodology: With the advent of both civilian and military real-time GPS satellite ephemeris and clock correction streams into the GPS user community, the question naturally arises: Which is better? The Jet Propulsion Laboratory and Navcom Technologies both have civilian data streams available to the public and the military is in the process of standing up the GPS Information Service (GPSIS) emanating from the GPS Operations Center (GPSOC). While civilian users only have civilian sources from which to choose, military users will have the capability to choose between the civilian data service and the military data service. To aid in making that choice, this paper will define a decision making criteria for choosing one service over another. The analysis will search for statistical significance in the differences in computed accuracy derived from the two services. The accuracy will be calculated as Signal-In-Space (SIS) using the Navigation Tool Kit as a Navigation Error modeling and analysis tool. Using a Paired Data Analysis (PDA) technique, differences in accuracy for a specific location will be analyzed. An initial check is made of the normality of the differences between the accuracies derived from the two data sets and then hypothesis testing is used to test the value of the differences. The null hypothesis is that there is no difference between the accuracies derived from the Military Data Stream and the Civilian Data Stream at a specified threshold level. The alternative hypothesis is that the accuracy derived from the Military Data Stream is better than the accuracy derived from the Civilian Data Stream for the given threshold. Anticipated Results: I intend to show that either the null hypothesis is supported or evidence is strong to reject it, using a 95% confidence threshold. Significance: This comparison technique is not unique to military and civilian error correction data; it can be applied to other error data sources as well. The outcome of this particular analysis however will shed light on problems inherent in error data processing and their statistical analysis. Lastly, the results of the analysis made lead to a better informed decision by the military, as to which data service to choose, when the choice must be made.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	48 - 57
Cite this article:	Driver, Ted, "Statistical Analysis of Military and Civilian Navigation Error Data Services," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 48-57.
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