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A Difference Test Method for Early Detection of Slowly Growing Errors in GNSS Positioning

Published online by Cambridge University Press:  09 August 2007

Shaojun Feng  and
Washington Ochieng
Shaojun Feng
Affiliation:
(Imperial College London)
Washington Ochieng*
Affiliation:
(Imperial College London)
*
(Email: [email protected])
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Abstract

Satellite based navigation system integrity monitoring is essential both for liability and safety critical services. The threats to system integrity are the potential failure modes that could occur at system, operational and user sensor levels. Research on identification, characterisation and modelling of such failure modes, suggests that failures that grow slowly over time (e.g. ramp error less than 2 m/s), also referred to as slowly growing errors (SGE) are the most difficult to detect early. Conventional snapshot algorithms detect SGEs when the test statistic crosses the threshold usually after relatively long periods of time. A recent concept based on the average of residuals over time has been found to have a significant weakness. This paper proposes a “difference test” algorithm capable of detecting SGEs early. In this method, the test statistic is the difference between the norm of current residuals and the norm of the residuals at a previous epoch. The distribution of the test statistic is over-bounded by a normal distribution whose parameters are derived from two Chi-distributions. Results show that the new algorithm results in a significant reduction in detection time compared to conventional methods.

Keywords

GNSSSystem IntegritySlowly growing errors
Type
Research Article
Information
The Journal of Navigation , Volume 60 , Issue 3 , September 2007 , pp. 427 - 442
Copyright
Copyright © The Royal Institute of Navigation 2007

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References

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