exchanges and cooperation, so as to improve the availability and stability of multi-GNSSs.
- Compatibility and interoperability are beneficial to GNSS providers and receiver manufacturers and even more favorable to users. In order to strengthen compatibility and interoperability, multiple GNSS providers should explore having exchanges and cooperation, and implementing technical research together to explore all possible solutions to realize interoperability.
- Interchangeability is a stronger and more specific goal than either compatibility or interoperability. It has already aroused multiple GNSS providers’ attention because it would enable GNSS users to estimate their longitude, latitude, altitude, and time offset based on any four satellites chosen from the interchangeable constellations. GNSS interchangeability is more a policy issue than simply a technical issue. Unswerving efforts should be made by multiple GNSS providers on GNSS interchangeability. This is especially important in regard to safety of life applications.
- During the GNSS construction and development process, it is essential to establish a global performance monitoring and assessing system, aiming to continuously monitor systems, improve service reliability, and improve performances. Because different GNSS providers and resources from different regions worldwide are involved in this issue, enhancing international exchanges and cooperation is quite important to realize the objective.
- GNSS space- and ground-based augmentation can effectively improve the performance of satellite navigation and positioning services. GNSS augmentation systems have to consider accuracy, continuity, availability, and integrity simultaneously. It is mutually beneficial for the BeiDou system and GPS system to enhance exchanges and cooperation between wide area augmentation systems.
- The BeiDou system and GPS system share the common responsibility to resist illegal interference with satellite navigation systems, which is also shouldered by governments, industry entities, and users from all countries. Interference-free environments are also the goal pursued by all users. Technical discussions can be conducted regarding interference identification, detecting, and positioning issues, while interference resistant solutions can be explored from system design, terminal applications, and other broader aspects.
- Certification of GNSS for use in aircraft landing has already taken place for GPS L1 signals in many parts of the world. However, it remains a very challenging enterprise. As new regions seek to certify the use of GNSS, it is essential to draw on the lessons learned from previous experiences. Prototyping and careful analysis of the results are important starting points. Experience with these prototype signals and the environ-