THE SATELLITE NAVIGATION SYSTEMS – STATUS, PROBLEMS, FUTURE

The satellite navigation systems are very important for the contemporary navigation, including and maritime navigation. Currently, there are several satellite navigation systems, used actively for navigation. There are several systems, which are currently being constructed. To provide the necessary coordinates and other navigation dates, they use geodetic reference systems (GRS). GRS are systems of parameters, describing the Earth as a complex geometric and physical figure.

These parameters are defined based on the large amount of geodetic, astronomical, gravimetric, Doppler, geomagnetic and others measurements, related to the determination of the figure of the Earth. In world practice, including and satellite navigation systems, are used parameters of several GRS systems - of US, Russia, China, India and others.

Can be mentioned that during 1979 was developed by the International Association of Geodesy and Geophysics (IUGG) international GRS system, which is recommended for application in various geodetic activities. This system is known as GRS 1980. There are some differences in the values of some of the corresponding parameters of the various GRS due to different Earth measurement databases, which are used for their determination.

These parameters are continuously specified during the performing of every subsequent Earth measurement and adjusted so that GRS systems to be modified without changing of their abbreviations. There is an irreversible trend regarding getting near of values on corresponding parameters in the different GRS to the internationally accepted, moreover these differences are negligible.