* Satellite navigation is based on the use of range measurements between navigational satellites and the user. Information about the satellite's coordinates is given to the user through a navigation signal. Range measurements are based on the calculation of the receiving signal time delay compared with the signals generated by the user equipment. * Currently, there are four global systems viz., GPS from the USA, GLONASS from Russia, Galileo from the European Union, and BeiDou from China. In addition, there are two regional systems viz., NavIC from India and QZSS from Japan. * Global navigation system caters to the users in the entire world, whereas the regional navigation system caters to the users in the limited service area. Hence, option (D) is the correct answer.