Availability and Continuity of Accuracy on Satelllite Navigation Systems

Abstract

This paper describes reliability performance of satellite navigation systems, such as US GPS (Global Positioning System) and Russian GLONASS (Global Navigation Satellite System), with an emphasis on computation methods to estimate availability and continuity of positioning accuracy achieved by the system. Computation methods for reliability performance indicators related to positioning accuracy must be considered carefully because of the difference to those for conventional ground-based navigation systems, i.e., positioning accuracy are largely affected by relative movement between the user and orbitting satellites.

Availability and continuity of accuracy are defined quantitatively. Computation examples are also shown and following facts would be made clear; (i) increase and decrease of the number of visible satellites have a large impact on the level of availability and continuity of accuracy; (ii) the expected continuity does not increase straightforwardly with respect to the vertical accuracy requirement and/or the number of geostationary satellites for augmentation while the availability does. The results are available for performance estimation and operational system design of satellite navigation systems which employ various satellite constellations with and without augmentation alternatives.