Integration of all available satnav signals for better performance and reliability is an important requirement for all users. Integration of GPS and GLONASS was important in the presence of Selective Availability (SA) and in post-SA scenario this helped in reduced visibility conditions. In presence of SA, use of GLONASS satellites in an integrated mode with GPS showed definite improvement in position solution, however, use of standalone GLONASS was restricted by constellation status. With removal of SA from GPS signal it was found that, presence of GLONASS satellite(s) improves satellite geometry and in certain cases the navigational accuracy. Integrated operation of GPS and GLONASS for use and popularization of GLONASS was seriously impaired by GLONASS availability since mid 2001, as number of active GLONASS satellites in the constellation decreased. Plans of modernization of GLONASS started in 2004; it was announced by the authorities that a complete operating constellation of 24 satellites would be provided by 2009. Users would expect to obtain the reflection of such improvement, particularly from geographical locations like India. Even in the light of the developing Galileo, the circumstances make one feel that users may have to wait for few more years to have access of Galileo. Thus, GLONASS may continue to be only supplementary system to GPS for quite some time from now. This paper firstly shows the results of a long term (1998 - 2001) study on effects of GLONASS satellite signals for positioning applications and then reviews the GLONASS modernization plan and its implementations during 2004 - 2010.
展开▼
