6. Conclusion on GNSS

Coverage and availability

The main limitations of GNSS are now well identified, and a great deal of work is being done to remedy them. The continuity of the "location" function is becoming such an issue that many scientific and industrial communities are involved in the "battle". All this is probably due to the success of GPS and its limitations in terms of coverage, availability, reliability and accuracy. This wouldn't be so bad if these limitations weren't in fact concentrated in specific environments: all characteristics degrade at the same time, making GNSS inoperable. This is why everyone is seeking either to improve their performance, or to complement them with other systems that take over in environments where GNSS doesn't work well (this is known as hybridization).

Potential GNSS-based solutions...