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{{Article Infobox2
{{Article Infobox2
|Category=Fundamentals
|Category=Other SBAS
|Title={{PAGENAME}}
|Editors=GMV
|Authors=GMV
|Level=Basic
|Level=Basic
|YearOfPublication=2011
|YearOfPublication=2011
|Logo=GMV
|Logo=GMV
|Title={{PAGENAME}}
}}
}}
SBAS systems are spreading out all over the world. More and more, it is believed that upon dual-frequency SBAS service provision, a seamless navigation will be possible from and to any two locations in the world.
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 [http://www.novatel.com/ Novatel] was awarded <ref>[http://findarticles.com/p/articles/mi_m0BPW/is_2_13/ai_n27573643/ NovAtel gains China order, GPS World, Feb. 2002]</ref> 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 <ref name="GSBAS/SBAS">[https://www.icao.int/APAC/APAC-RSO/GBASSBAS%20Implementation%20Workshop/3-5_GBAS-SBAS%20Implementation%20in%20China%20(X%20Li).pdf GSBAS/SBAS Implementation in China], ICAO ASIA/PACIFIC REGIONAL GBAS/SBAS WORKSHOP, Seoul, ROK, 3~5 June 2019</ref>.
 
==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. <ref name="Update_Beidou">[https://www.unoosa.org/documents/pdf/icg/2017/05_icg12.pdf 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</ref>
 
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. <ref name="Update_Beidou/>
 
During 2019, efforts were focused on improving the ground monitoring stations network. <ref name="Update_Beidou"/>
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. <ref name="Advances_Beidou">[https://satellite-navigation.springeropen.com/articles/10.1186/s43020-020-00010-2 Advances in BeiDou Navigation Satellite System (BDS) and satellite navigation augmentation technologies], Li, R., Zheng, S., Wang, E. et al.</ref>


==SBAS in the World==
==Space segment==
From all the SBAS systems in the world, three are already operational ([[WAAS General Introduction|WAAS]], [[MSAS General Introduction|MSAS]], [[EGNOS General Introduction|EGNOS]]), three are under implementation ([[GAGAN]], [[SDCM]], [[SNAS]]) while others are under feasibility studies, for instance SACCSA.
The actual space segment of BDSBAS is composed of 3 GEO satellites <ref name="Constellation">[http://www.csno-tarc.cn/en/system/constellation BeiDou Constellation Status]</ref>
{| class="wikitable" style="vertical-align:bottom;"
|-
! <br />PRN
! <br />SVN
! <br />SatelliteType
! <br />LaunchDate
! <br />SatStatus
! <br />Service Signal
! <br />Position
|-
| <br />130
| <br />GEO-01
| <br />BDS-3
| <br />2018-11-01
| <br />Testing
| <br />B1C/B2a
| <br />140°E
|-
| <br />143
| <br />GEO-03
| <br />BDS-3
| <br />2020-06-23
| <br />Testing
| <br />B1C/B2a
| <br />110.5°E
|-
| <br />144
| <br />GEO-02
| <br />BDS-3
| <br />2020-03-09
| <br />Testing
| <br />B1C/B2a
| <br />80°E
|}


<gallery widths="200px">
==Performances==
Image:SBAS_in_the_world.png|Some SBAS systems either operational, under development or under study
The design performances of BDSBAS are <ref name="Update_Beidou"/>:
</gallery>
{| class="wikitable" style="vertical-align:middle;"
|-
| rowspan="4" | Service accuracy (95%)
| rowspan="2" | Position accuracy
| Single frequency
| Double frequency
|-
| H < 2.5 m, V < 4.0 m
| H < 1.5 m, V < 2.0 m
|-
| Timing accuracy
| colspan="2" |10 ns
|-
| Velocity accuracy
| colspan="2" | 0.1 m/s
|-
| rowspan="3" | Service reliability
| Availability
| colspan="2" | > 99 %
|-
| Integrity
| colspan="2" | Alarm time: 6s<br />Risk probability: 10-7/approach<br />(threshold: H 40m, V 10-15m)
|-
| Continuity
| colspan="2" | Risk probability: 10-6/15s
|}


==SNAS==
Observed performance of B1C and B2a SBAS signals in 2019 <ref name="Update_2019">[https://www.unoosa.org/documents/pdf/icg/2019/icg14/05.pdf 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</ref>:
The People's Republic of China is developing its own SBAS, called Satellite Navigation Augmentation System ([[Work in Progress:SNAS|SNAS]]).  The company [http://www.novatel.com/ Novatel] was awarded with a contract for the provision of 12 receivers for the phase 2 of the development in 2002.<ref>[http://findarticles.com/p/articles/mi_m0BPW/is_2_13/ai_n27573643/ NovAtel gains China order, GPS World, Feb. 2002]</ref> These stations would complement the 11 ones already installed around Beijing for the phase 1.
* Global coverage.
There is little public information available on this development.
* 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%)


==Notes==
[[File:BDSBAS_availability.png|thumb|center|upright=2.0|Service availability of B1C and B2a signals <ref name="Update_2019"/>]]
<references group="footnotes"/>


==References==
==References==

Latest revision as of 09:32, 1 October 2021


Other SBASOther SBAS
Title SNAS
Edited by GMV
Level Basic
Year of Publication 2011
Logo GMV.png

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%)
Service availability of B1C and B2a signals [6]

References

  1. ^ NovAtel gains China order, GPS World, Feb. 2002
  2. ^ GSBAS/SBAS Implementation in China, ICAO ASIA/PACIFIC REGIONAL GBAS/SBAS WORKSHOP, Seoul, ROK, 3~5 June 2019
  3. ^ 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
  4. ^ Advances in BeiDou Navigation Satellite System (BDS) and satellite navigation augmentation technologies, Li, R., Zheng, S., Wang, E. et al.
  5. ^ BeiDou Constellation Status
  6. ^ 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
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