Global Satellite Navigation Using Both GPS and Glonass

Both the U.S. and Soviet Union are developing global satellite navigation systems which are capable of pin-pointing a user anywhere on or near the surface of the earth. Under ideal conditions, both systems provide comparable accuracies. GPS and GLONASS, though different, use the same operating principles and have a great deal in common. Each system has some advantages over the other and both would benefit from larger constellations. This is especially true with loss of signals due to obstructions or satellite failures. A receiver which uses both systems is optimal. It takes advantage of a constellation with twice as many satellites and benefits from the two redundant, independent systems. The large combined constellation increases the probability of having enough satellites to navigate and speeds up geodetic and kinematic surveying. Perhaps, more important, the larger number of satellites from the two independent systems permits high confidence, receiver autonomous integrity monitoring (RAIM) for safe navigation under all conditions. This paper compares the two systems, discusses the advantages of a combined receiver and describes the design of an integrated GPS/ GLONASS receiver. The paper goes on to describe the operational status of GLONASS and compares the performance of GLONASS and GPS using actual measured data.