A Study of Integrity Indicators in Outdoor Navigation Systems for Modern Road Vehicle Applications

Resumen

The applicability of navigation systems in outdoor scenarios strongly depends on the level of reliability that the user can have on the provided pose estimation. For this reason,navigation systems must provide integrity values, representative of this level. In the current literature, there are two main possibilities for the provision of integrity in navigation, RAIM (or Receiver Autonomous Integrity Monitoring) and SBAS (Satellite Based Augmentations Systems) based integrity.Both options supply integrity estimators based exclusively on satellite navigation, what results in a lack of precise integrity information during absences of satellite visibility. In addition,despite the fact that modern navigation systems employ more sensors aboard the vehicle, such as odometry or inertial sensors,the methods previously mentioned do not take into account the resulting accuracy of pose estimates based on multi-sensor fusion. This paper presents a comparison between the SBAS based HPL (Horizontal Protection Level) and HIT (Horizontal Integrity Threshold), a multi-sensor based value representative of the joint pose estimates. Real tests show its suitability to mitigate the lacks of traditional integrity indicators. The paper concludes with a revision of integrity provision in next generation navigation systems.