What is GPS?
- The Global Positioning System is a satellite-based navigation system developed by the U.S. Department of Defence (USDOD) for military use which was made available for civilian applications in 1983.
- The satellites orbit the earth in six, nearly circular, orbits at an altitude of 20,200km (10,000 nautical miles) with four operational satellites plus a spare in each.
- Each orbital plane is equally spaced about the equator and inclined at 64.8 degrees. The satellites transmit highly accurate, real-time, worldwide navigation information at a frequency of 1598-1609 MHz.
What is GLONASS?
- The GLONASS navigation system was developed by the Russian government, initially for military use and now available for unlimited commercial access.
- GLONASS has satellites in three orbits at an altitude of 19,100km (10,313 nautical miles), transmitting precise time and navigation information at a frequency of 1598-1609 MHz
How GPS is used to calculate accurate local time
- Each satellite continuously transmits a unique code message format which includes precise orbital data and highly accurate time information derived from an atomic clock.
- The Wharton 488HS-GPS or 488HS-GLONASS receiver simultaneously receives the signals from several satellites.
- The receiver calculates the exact position of each of the satellites and by triangulation, the receiver’s geographical location together with a precise local time.