Integrity Monitoring System Design for the Multi-GNSS Analysis Centre Software

Real-time monitoring of GNSS satellite status, measurement data, ground infrastructure network and augmentation corrections for PPP-RTK with timely alarm messages in case of failures.

The Challenge

The Analysis Centre Software (ACS) forms the primary utilisation pathway for research outputs conducted within the CRCSI Positioning Program. This project aimed to develop an integrity and continuity design concept in the context of the multi-GNSS ACS PPP-RTK system based on the un-differenced, un-combined processing framework. Integrity equates to the degree of trust that can be placed in the information provided. Integrity also includes the ability of the system to provide timely and valid warnings to the user when the system cannot and must not be used for the intended purpose. Research in integrity monitoring for GNSS positioning and navigation using fault-tree analysis, threat modelling, and fault detection and exclusion has been conducted for aviation applications. But there are fundamental differences between aviation requirements and non-aviation applications using the PPP-RTK method.


The project partners were Geoscience Australia, the Royal Melbourne Institute of Technology (RMIT), Land Information New Zealand (LINZ) and University of NSW (UNSW).

The Solution

This project was a sub project of the On-going Development of the Multi-GNSS Analysis Centre Software. This project developed a concept for integrity monitoring at the ACS level to protect users from failures of GNSS satellites and transmission of erroneous and/or inaccurate corrections. To achieve this, a fault-tree analysis was conducted to identify the probabilities of fault events that could affect the overall quality of the PPP-RTK solutions. Integrity quality indicators for the ACS were proposed. The project was broken into three tasks:

  1. Integrity monitoring concepts and requirements for PPP-RTK.
  2. Fault-tree analysis for the ACS.
  3. Design of an integrity concept for the ACS PPP-RTK method.

The project outputs were:

  • A basic integrity concept for the ACS to provide users with integrity measures at the system level. When combined with information at the user level, users can then perform fault detection and exclusion as well as compute protection levels for precise positioning.
  • A basic fault-tree analysis to identify and attempt to quantify all possible failure modes within the ACS.

PPP-RTK, provides high accuracy (cm-dm level) positioning using both code and carrier phase measurements. Providing a guaranteed level of integrity has remained a lesser priority. Although there are emerging applications that have increased demands for high positioning accuracies, integrity is also becoming a critical requirement, particularly where safety is important. Absence of integrity information would ultimately constrain the adoption of augmented GNSS in several emerging industry and market sectors. The proposed integrity monitoring system concept is ultimately responsible for providing real-time monitoring of the GNSS satellite status, measurement data, ground infrastructure network and augmentation corrections for PPP-RTK with timely alarm messages in case of failures. It is imperative to detect such errors for providing high accuracy positioning solutions with high integrity. This research was timely and made a significant contribution to the ACS capability in particular and the PPP-RTK method more generally. The outcomes from this project formed a basic discovery of possible innovative solutions to provide high accuracy GNSS positioning service with complementary integrity information. This was built into a pitch for funding beyond the life of the project.


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