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SNAS
| Other SBAS | |
|---|---|
| Title | SNAS |
| Edited by | GMV |
| Level | Basic |
| Year of Publication | 2011 |
The People's Republic of China is developing its own SBAS, called BeiDou satellite-based augmentation system (BDSBAS and formerly Satellite Navigation Augmentation System (SNAS)) to provide SBAS services in China and sorrounding regions. In 2002, the company Novatel was awarded [1] with a contract for the provision of 12 receivers for the phase II of the development, and the receivers have already been delivered. These stations would complement the 11 ones already installed in and around Beijing for the phase I of the program.
BDSBAS is integrated in the BeiDou system and uses BDS-3 type satellites to broadcast SBAS L1/L5 signal, augmenting BDS and GPS. If they are recommended by ICAO SARPs, Galileo E1C/E5a and GLONASS L1/L3 will also be considered [2].
Development
In october 2017, 3 PRN codes (130, 143 and 144) were assigned at L1C/A and L5 for the BDSBAS system. The system was also recognized as an official SBAS provider in the ICAO family, being given its SBAS service provider identifier and the UTC standard identifier. The space segment is being defined to be conposed of three BD-3 GEO satellites (80º E, 110.5º E and 140º E). The ground segment is composed of an Operation and Control Center, Data Centers, Uplink Stations and Monitoring Stations. SBAS terminals would be able to receive RNSS navigation messages and wide area differential integrity information broadcast by GEO satellites. [3]
In 2018, the first BDS-3 GEO satellite was launched in November 1, 2018 onboard a Long March 3B and the broadcast of BDSBAS signal started in November 9, 2018, beginning the integration and test phase. [3]
During 2019, efforts were focused on improving the ground monitoring stations network. [3] The system is still being tested today and therefore cannot yet provide services for civil aviation but it is expected to initially provide APV-I service, and later on CAT-I service in China. [4]
Space segment
The actual space segment of BDSBAS is composed of 3 GEO satellites [5]
PRN |
SVN |
SatelliteType |
LaunchDate |
SatStatus |
Service Signal |
Position |
|---|---|---|---|---|---|---|
130 |
GEO-01 |
BDS-3 |
2018-11-01 |
Testing |
B1C/B2a |
140°E |
143 |
GEO-03 |
BDS-3 |
2020-06-23 |
Testing |
B1C/B2a |
110.5°E |
144 |
GEO-02 |
BDS-3 |
2020-03-09 |
Testing |
B1C/B2a |
80°E |
Performances
The design performances of BDSBAS are [3]:
Service accuracy (95%) |
Position accuracy |
Single frequency |
Double frequency |
H < 2.5 m, V < 4.0 m |
H < 1.5 m, V < 2.0 m | ||
Timing accuracy |
10 ns | ||
Velocity accuracy |
0.1 m/s | ||
Service reliability |
Availability |
> 99 % | |
Integrity |
Alarm time: 6s Risk probability: 10-7/approach (threshold: H 40m, V 10-15m) | ||
Continuity |
Risk probability: 10-6/15s | ||
Observed performance of B1C and B2a SBAS signals in 2019 [6]:
- Global coverage.
- System service availability: >87%.
- Positioning accuracy: 2.4 m horizontally, 4.3 m vertically.
- Velocity measurement accuracy: 0.06 m/s
- Timing accuracy: 19.1 ns (95%)
References
- ^ NovAtel gains China order, GPS World, Feb. 2002
- ^ GSBAS/SBAS Implementation in China, ICAO ASIA/PACIFIC REGIONAL GBAS/SBAS WORKSHOP, Seoul, ROK, 3~5 June 2019
- ^ a b c d Update on BeiDou Navigation Satellite System, China Satellite Navigation Office, Twelfth Meeting of the International Committee on Global Navigation Satellite Systems, 2-7 December 2017 Kyoto, Japan
- ^ Advances in BeiDou Navigation Satellite System (BDS) and satellite navigation augmentation technologies, Li, R., Zheng, S., Wang, E. et al.
- ^ BeiDou Constellation Status
- ^ a b Update on BeiDou Navigation Satellite System (BDS), Peng JIA, China Satellite Navigation Office, 14th Meeting of the International Committee on Global Navigation Satellite Systems, 2019-12-09