RFGPS vs GLONASS: Detailed Comparison of Satellite Navigation Systems
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This tutorial explores the fundamentals and applications of the GPS (Global Positioning System) and GLONASS (Global Navigation Satellite System) technologies. We will cover the basics of each system, highlight their key differences, and touch upon related technologies like A-GPS.
This guide also provides links to manufacturers of GPS modules, chips, and components.
GPS and GLONASS: An Overview
Both GPS and GLONASS are satellite-based navigation systems that enable precise positioning and tracking.
- GPS: Developed by the United States, introduced in 1978.
- GLONASS: Developed by the Soviet Union, introduced in 1982.
Modern devices often incorporate both GPS and GLONASS capabilities to enhance accuracy and reliability. These systems rely on microwave signals transmitted by satellites to determine location.
The table below provides a detailed comparison of GPS and GLONASS satellite navigation systems, focusing on satellite orbits and carrier signals.
Both GPS and GLONASS satellites transmit data at a relatively slow rate of 50 bits per second, which can lead to delays in acquiring positioning information. To address this, A-GPS (Assisted GPS) and A-GLONASS systems were developed.
A-GPS and A-GLONASS leverage faster data connections (e.g., via LTE or GSM/CDMA base stations) to obtain assistance data at speeds up to 100 Mbps. This significantly speeds up the process of acquiring initial positioning information.
GPS vs GLONASS: Key Differences
| Specifications | GPS | GLONASS |
|---|---|---|
| Orbital planes | 6, spaced by 60 degrees | 3, spaced by 120 degrees |
| Satellites per orbital plane | 4, unevenly spaced | 8, evenly spaced |
| Orbital plane inclination | 55 degrees | 64.8 degrees |
| Orbital radius | 26560 Km | 25510 km |
| Orbital period | About 11 hours and 58 minutes (1/2 of sidereal day) | 11 hours and 16 minutes |
| Repeat ground track | Every sidereal day | Every 8 sidereal days |
| Carrier signals | L1 band: 1575.42 MHz, L2 band: 1227.60 MHz | L1 band: (1602 + k x 9/16) MHz, L2 band: (1246 + k x 7/16) MHz, where k is the channel number |
| Codes | Different for each satellite, C/A code on L1 and P-code on L1/L2 | Same for all satellites, C/A code on L1 and P-code on L1/L2 |
| Code frequency | C/A code - 1.023MHz and P-code 10.23 MHz | C/A code - 0.511 MHz and P-code 5.11 MHz (half that of GPS) |
| Clock data | Clock offset, frequency offset, frequency rate to calculate the difference between individual GPS satellite’s time and GPS system time. | Broadcasted Clock and frequency offset provides difference between time of GLONASS satellite and GLONASS system |
| Orbital data | Modified keplerian orbital elements every hour | satellite position, velocity and acceleration every half hour |
