EGNOS vertical protection level assessment

David Comby (1) , Rick Farnworth (2) , Christophe Macabiau (3)

1 French Air Force
2 Eurocontrol Experimental Centre
3 ENAC - Ecole Nationale de l'Aviation Civile

The EGNOS Signal In Space (SIS) performance is defined in terms of accuracy, integrity, continuity of service and availability. For Civil Aviation, those four components of the performance shall fulfill ICAO requirements (particularly stringent for the integrity). EGNOS is expected to be operational by the first quarter of 2004. One of the major issues for Civil aviation in the perspective of operating EGNOS, is to prove that the system is safe to use. In this context, the demonstration of the EGNOS compliance with the integrity requirements is of the utmost importance. This raises the following question : How to assess the integrity performance of the EGNOS SIS ? In the frame of Eurocontrol work supporting the operational validation of EGNOS, a number of techniques are under investigation to evaluate measurement data and provide an assessment of the integrity achieved. It is not expected, even using a combination of different techniques that compliance with integrity requirement will be exhaustively demonstrated as this would require an amount of data that is impracticable to collect. The main contributor to the integrity validation is the analysis performed during the system design. However, it is necessary to use techniques such as the one presented in this paper to examine the behavior of the protection level in relation to the position error in order to gain a better understanding of how the system is performing. This technique will also help to identify when the system is not performing as it should be, even during times when it appears to be functioning correctly. The aim of the work presented in this paper is to develop a methodology for the assessment of the EGNOS Vertical Protection Level (VPL). The presented analysis is based on the processing of data from the EGNOS System Test Bed that is received by a network of data collection stations distributed throughout Europe. The objective is to make a statistical analysis of the Vertical Position Error (VPE) that can be measured at the output of the data collection receivers. An estimated VPL can be computed from the position error data enabling an evaluation to be made as to whether the VPL provided by the EGNOS system is a conservative bound on the VPE or not. For a given processed data set, a confidence level in the VPL is defined as an estimated probability that the VPL is a bound of the VPE. The analysis aims to provide the confidence levels as indicators of the quality of the VPL over selected data sets.

Domaines: Traitement du signal et de l'image [eess.SP]; Traitement du signal et de l'image [eess.SP]

David Comby, Rick Farnworth, Christophe Macabiau. EGNOS vertical protection level assessment. ION GPS/GNSS 2003, 16th International Technical Meeting of the Satellite Division of The Institute of Navigation, Sep 2003, Portland, United States. pp 2783 - 2794. ⟨hal-01021722⟩