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GLONASS Performances
| GLONASS | |
|---|---|
| Title | GLONASS Performances |
| Author(s) | GMV |
| Level | Basic |
| Year of Publication | 2011 |
Equivalent to the Standard Positioning Service (SPS) and the Precise Positioning Service (PPS) of GPS, GLONASS provides a standard precision (SP) navigation signal and a high precision (HP) navigation signal. These signals are sometimes also referred to as Channel of Standard Accuracy (CSA) and Channel of High Accuracy (CHA), respectively.
One of the main objectives of the Global Navigation System (GNS) is to ensure GLONASS performance similar to GPS by the end of 2011. GLONASS traditional poorer performance was the culmination of several factors:[1]
- poorer on-board atomic clocks
- less stability and predictability in the satellite orbits (and therefore less accuracy in GLONASS broadcast ephemerides)
- fewer satellites providing signals
- operational control and ground monitoring segment limited to Russian territory.
The improvements carried out on the space, ground-based and user equipment segments have paid off, increasing five times the accuracy of GLONASS in the last years[2] and providing 100% availability in the Russia territorry and obtaining almost worldwide coverage.
GLONASS Availability
The very low number of operational satellites in the constellation (in 2001 there were only seven satellites) along with a ground segment limited to Russian territory, have been the main reasons of GLONASS poor availability performance. The modernization of the Ground Segment, including new monitoring stations (some of them outside the Russia) and especially the increase of the number of satellites in the constellation (In the present, GLONASS constellation consists of 27 satellites in orbit although only 23 of them are operational), have led to almost worlwide coverege and 100 % availability in the Russian territory.
The table included below, shows the increasing of the number of satellites and the availability performance (calculated as the percentage of time during which the condition PDOP ≤ 6 is valid at mask angles ≥ 5 deg) from the begining of 2007 to July 2011.[3]
| Date | Operational Satellites in constellation | Integral Availability Global | Integral Availability on Russian territory |
|---|---|---|---|
| 2011/07/06 | 23 | 99.5 % | 100 % |
| 2011/01/01 | 22 | 99 % | 100 % |
| 2010/01/01 | 15 | 73.6 % | 85.3 % |
| 2009/01/01 | 16 | 87.4 % | 96.6 % |
| 2008/01/01 | 12 | 48 % | 57.6 % |
| 2007/01/01 | 9 | 19.2 % | 26.3 % |
GLONASS accuracy
According to Revnivykh,[2] deputy director of the Russian space agency’s Mission Control Cente, GLONASS accuracy has five times improved in the last years. As it is shown in the figure on the right, in 2006 GLONASS Signal In Space Range Error (SISRE) at 1 sigma was in the order of 25 m. At the moment of this publication, July 2011, the accuracy of GLONASS is 6-7 metres, the same order as GPS.
As Anatoly Shilov said at the 5th international forum on satellite navigation yesterday, the accuracy of the Russian navigation system would have to be improved to 2-3 metres in the following years.