Developing a Framework for Image-Based Integrity

C. Larson, J. Raquet, M.J. Veth

Abstract:	The concept of navigation system integrity has been welldeveloped for the Global Positioning System (GPS). This concept and associated integrity monitoring processes focus on identifying, and ideally excluding, faulty measurements before they can corrupt the GPS position solution. The definition of an assured protection limit is also a GPS integrity requirement. It is an unfortunate fact that GPS signal availability cannot be guaranteed under all environmental or operational conditions. Image-based navigation has been shown to be a potential alternative to navigation in the absence of GPS. However, the concept of integrity in an image-based context has not been fully explored. Image-based measurements from a single camera are provided in pixel pairs for each target tracked, vice a single pseudorange measurement for each observed satellite, resulting in a different dimensionality in the measurement model equations. In addition, an image-based system is not always supported by a fixed constellation of measurement sources (e.g. available satellites), so there is the potential for a greatly varying number of overall measurements and possible measurement source geometries in a vision-based system. While an increase in the number of redundant measurements may aid integrity monitoring, it also may produce a higher probability that a measurement is faulty, increasing the importance of having a robust monitoring process. This paper investigates the extension of fundamental GPS autonomous integrity monitoring methodologies to develop a framework for integrity in image-based navigation. A relationship is derived between the horizontal position error and an associated test statistic in order to predict the least observable error source with the greatest influence on position error. Results are presented using a minimal subset of measurements in different geometries to demonstrate the influence of the two-dimensional image measurement error on the position error.
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:	778 - 789
Cite this article:	Larson, C., Raquet, J., Veth, M.J., "Developing a Framework for Image-Based Integrity," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 778-789.
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