GLONASS GPS "Galileo " Comparison of three systems

GLONASS and GPS have many differences: The first satellite launch different frequencies. GPS satellite signals using code division multiple access system, each satellite signal frequency and modulation in the same way, the signals from different satellites by the distinction between the different pseudo-code. The GLONASS system uses frequency division multiple access, satellite distinguished by different frequencies, each frequency of the same pseudo-random code. Since the carrier frequency of different satellites, GLONASS satellite navigation system can also prevent the interference by the enemy, therefore, have a stronger anti-interference ability. Second, the coordinates are different. GPS uses the World Geodetic System (WGS-84), and the former Soviet Union, GLONASS geocentric coordinate system used (PE-90). Third, the time standard different. GPS systems are associated with the Universal Coordinated Time, and GLONASS are associated with the Moscow standard time.

"Galileo" catch up "Galileo" system is planned to build a new generation of civil European global satellite navigation system, the system 2008 is expected to be completed and put into operation. According to the plan, "Galileo" project will cost about 27 billion constellation of 30 satellites. Medium Earth orbit satellites used, evenly distributed in the height of about 2.3 million kilometers of three orbital planes, including 27 working star constellation, plus three backup satellites. A typical system is the signal relay function, namely the user receiver data transfer via a special contact or other relay system to achieve, for example through mobile communication network to achieve. "Galileo" system, the receiver can not only accept the signal, and can accept the G