GNSS Integrity Concepts for Maritime Users

Some of the most important parameters of operational requirements for Global Navigation Satellite System (GNSS) are integrity, continuity, accuracy, availability and coverage. These requirements, most strictly formalized in aviation, are based on risk analysis, considering risk exposure time and critical risk exposure time. However, the GNSS user requirements in maritime domain are still not clearly set. GNSS offers worldwide coverage at a sufficient position data quality and though other means of ship's position fixing are available at sea, the use of GNSS devices is generally the most preferred method of producing valid position data. Primary means for electronic position fixing currently in use in majority of merchant ships are shipborne autonomous GPS receivers or DGPS IALA receivers. More advanced GNSS receivers able to process signals from GPS, GLONASS, Chinese Beidou, European Galileo, regional Indian IRNSS, and satellite based augmentation systems (SBAS) are still rare. But it is expected that such combined or multi-system receivers will soon become more common in maritime transport.To be prepared for a malfunction of any GNSS devices for maritime applications and e-Navigation specifically, their state of the art integrity monitoring should be developed and standardized analogously to other transport domains. The issues of existing requirements, performance standards, and future concepts of maritime GNSS integrity are discussed in this paper.