"GLONASS GLONASS" is the Russian " GLOBAL NAVIGATION SATELLITE SYSTE" acronym. The role is similar to the US GPS and the European Galileo satellite positioning system. The system consists of three segments, satellite constellation, ground monitoring station and user equipment. The main services include determining land, sea and air targets coordinates and velocity information. GLONASS can all-day, continuously provide high-precision three-dimensional position, three-dimensional velocity and time information for a variety of military and civilian users around the sea and air as well as near-Earth space. Positioning, velocity and timing accuracy of GLONASS is better than the GPS Selective Availability (SA) .
The European Galileo system is the new generation of European civil global satellite navigation system, the system constitutes of 4 parts, the space segment, the environment segment, the ground segment, the user segment. Galileo provides five kind of service: OS, similar to GPS SPS (free of charge), SoLS, CS, PRS, and SAR.
GPS stands for Global Positioning System. GPS provides standard positioning service (SPS) and precise positioning service (PPS).