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The [[COMPASS General Introduction|Compass Navigation Satellite System (CNSS)]], also named BeiDou-2,<ref name=Chinese_today>[http://www.sinodefence.com/space/satellite/compass-beidou2.asp Compass Satellite Navigation System (Beidou), on Sinodefence.com, updated on August 6th, 2011.] </ref> is China’s second-generation satellite navigation system that will be capable of providing positioning, navigation, and timing services to users on a continuous worldwide basis<ref name=Chinese_today/><ref name=COMPASS_Wiki>[http://en.wikipedia.org/wiki/Compass_navigation_system COMPASS Navigation system in Wikipedia]</ref>.
The [[COMPASS General Introduction|BeiDou Navigation Satellite System (BDS)]], also known as COMPASS or BeiDou-2,<ref name=BDS_STATUS>[http://www.filasinternational.eu/sidereus-project/pdf/02.pdf Compass/BeiDou Status], Jun Shen, BNStar Navigation Technology & System, Inc., Rome (Italy), June 11, 2009.</ref> is China’s second-generation satellite navigation system<ref name=BDS_STATUS/><ref>[https://en.wikipedia.org/wiki/Beidou_Navigation_Satellite_System BeiDou Navigation Satellite System in Wikipedia]</ref> that will be capable of providing positioning, navigation, and timing services to users on a continuous worldwide basis<ref name=BDS_WORLDWIDE>[http://www.insidegnss.com/node/3590 BeiDou China’s Rapidly Emerging GNSS, InsideGNSS, May/June 2014]</ref>.
The system is being deployed using an incremental approach and full operational capability is expected to be reached by 2020. The COMPASS System has been designed to reach accuracy levels similar to those of GPS and Galileo Open Service: positioning accuracy within 10 meters, timing accuracy within 20 ns and velocity accuracy within 0.2 meters per second.
The system is being deployed using an incremental approach and full operational capability is expected to be reached by 2020<ref name=BDS_WORLDWIDE/>. The BeiDou System has been designed to reach accuracy levels similar to those of GPS and Galileo Open Service: positioning accuracy within 10 meters, timing accuracy within 50 ns and velocity accuracy within 0.2 meters per second<ref name=BDS_PERFO>[http://interact.beidou.gov.cn/interact/download.service?attachment=2013/12/26/20131226b8a6182fa73a4ab3a5f107f762283712.pdf BeiDou System, Open Service Performance Standard], China Satellite Navigation Office, Version 1.0, December 2013</ref>.


==COMPASS Performances==
==BeiDou Performances==


The BeiDou-1 system was established in 2003 for the area of the greater China and provided navigation, communication and timing services with performance characteristics as follows:<ref name='Rome'>[http://www.filasinternational.eu/sidereus-project/pdf/02.pdf Jun Shen, ''COMPASS/Beidou-China’s GNSS'', BNStarNavigation Technology & System, Inc., Rome, June 11th, 2009]</ref>:
===BeiDou Navigation Test System (BeiDou-1)===
 
The BeiDou-1 system was established in 2003, after the successful launch of BeiDou-1C satellite, for the area of the greater China and providing navigation, communication and timing services with performance characteristics as follows:<ref name=BDS_STATUS/>:


* Positioning: 100m (1σ); 20m (1σ, with reference stations).
* Positioning: 100m (1σ); 20m (1σ, with reference stations).
Line 17: Line 19:
* Timing: 20 ns.
* Timing: 20 ns.


===BeiDou Navigation Satellite System (BeiDou-2)===


The Initial Operational Service of COMPASS was officially declared in December 2011, for which the initial performances as reported in the Munich Satellite Navigation Summit of 2012 are:
The Initial Operational Service of BeiDou System was officially declared in December 2011, for which the initial performances as reported in the Munich Satellite Navigation Summit of 2012 were:
* Service coverage area: regional
* Service coverage area: regional
* Positioning accuracy: 25 meters horizontally adn 30 meters vertically
* Positioning accuracy: 25 meters horizontally adn 30 meters vertically
* Timing accuracy of 50 ns
* Timing accuracy of 50 ns
*Velocity accuracy of 0.4 m/s
* Velocity accuracy of 0.4 m/s


These performances are expected to improve as the number of satellites in orbit increase and the user segment evolves.
These performances are being improved as the number of satellites in orbit increase and the user segment evolves.


The global BeiDou system will be built by 2020 and it is being designed to offer the following performances for  each [[COMPASS Services]]<ref  name=BEIDOU_MUNICH_2011>China Satellite Navigation Office, Development of BeiDou Navigation Satellite System, Munich Satellite Navigation Summit, 2011</ref><ref name=BDS_STATUS/><ref name=BDS_WORLDWIDE/><ref name=BDS_PERFO/><ref>[http://www.beidou.gov.cn/2013/09/29/2013092903db7281fa3f43b9aaeb1cb65d606b1a.html Ran Chengqi: The Construction and Development of Beidou Navigation Satellite System]</ref>:


The global COMPASS system will be built by 2020<ref name="Compass-IGSO3">[http://business.globaltimes.cn/industries/2011-04/642763.html ''China completes basic Beidou (Compass) Navigation Satellite System''], 2011-04-10 by Globaltimes.cn</ref> and it is being designed to offer the following performances for  each [[COMPASS Services]]<ref  name=BEIDOU_MUNICH_2011>China Satellite Navigation Office, Development of BeiDou Navigation Satellite System, Munich Satellite Navigation Summit, 2011</ref><ref name='Rome'/>:
* ''Open service'': a free service for civilian users with positioning accuracy better than 10 meters, velocity accuracy better than 0.2 m/s and timing accuracy better than 50 nanoseconds, considering 95% probability.


* ''Open service'': a free service for civilian users with positioning accuracy of within 10 meters, velocity accuracy of within 0.2 m/s and timing accuracy of within 20 nanoseconds. The Open Service is planned to be available a few years ahead of the system full operational capability;  
* ''Authorized service'': a licensed service with higher accuracy even in complex situations for authorized and military users only;  


* ''Authorized service'': a licensed service with higher accuracy even in complex situations for authorized and military users only.
* ''Wide area differential positioning service'': with positioning accuracy of sub-meter and meter for dual-frequency and single-frequency receivers;
 
* ''Wide area differential positioning service'': with positioning accuracy of 1 m.


* ''Short message service (SMS)'': up to 120 Chinese characters.
* ''Short message service (SMS)'': up to 120 Chinese characters.


====Combined Services Performances====


[[File:CurrentCompassSignals.png‎|<b>Table 1</b>: COMPASS Signals Characteristics<ref name=COMPASS_ION>"Positioning Performance Analysis of The Current COMPASS Constellation", M. Lu, J. Guo, Tsinghua University, COMPASS Workshop, ION GNSS 2011</ref>|400px|thumb]]
[[File:BeiDou_PDOP.png‎| PDOP of GPS , BeiDou and combined GPS+BeiDou (elevation =7.5)<ref name=BDS_GPS>The Comparison on the Positioning Performance Between BeiDou and GPS: Y. Xu, S. Ji, W. Chen, D. Weng, Y.Xu, W. Chen, D. Weng, The Hong Kong Polytechnic University, Hong Kong; S. Ji, China University of Petroleum, China, ION GNSS 2013.</ref>|400px|thumb]]
 


Preliminary performance figures were presented in the COMPASS Workshop, integrated in the ION GNSS 2011 Conference.
Preliminary performance figures were presented in the BeiDou Workshop, integrated in the ION GNSS 2013 Conference. The BeiDou constellation available at the time already provided many visible satellites as GPS (BeiDou: 8, 9, 10, 11, 12, 13; GPS: 6, 7, 8, 9, 10, 11, 12, 13), but the values of PDOP are bigger than that of GPS (average values, BeiDou: 2.076, GPS: 1.694), as depicted in the figure<ref name=BDS_GPS/>.
The COMPASS constellation available at the time (referred to as "3+3", standing for 3 GEO Satellites and 3 IGSO satellites), operational in July 2011, includes the signals depicted in Table 1.


These results show that a combined COMPASS("3+3")+GPS constellation provides:
The presented results shown that a combined BeiDou+GPS constellation provides<ref name=BDS_GPS/>:
* higher availability: up to 14 satellites were visible in the test conditions (compared to up to 9 with GPS only);
* Higher availability: up to 15 satellites were visible in the test conditions (compared to 6 in some cases of GPS only);
* better geometry: the PDOP for the combined constellation was lower than the PDOP for each individual constellation.
* Better geometry: the PDOP for the combined constellation was lower than the PDOP for each individual constellation;
* Better precision: the precisions of GPS are slightly better than that of BeiDou in both horizontal and vertical direction, but the combined solution GPS+BeiDou got the best performance in all direction.


The results show that the accuracy of the combined solution (GPS and current COMPASS) is in general worse than the single GPS Solution - even though in the same order of magnitude. This was explained by the differences between systems and the preliminary status of the COMPASS constellation which is still expected to improve their satellite clocks and orbits accuracy as it reaches full operational capability.


==Notes==
<references group="footnotes"/>
==References==
==References==
<references/>
<references/>

Revision as of 10:48, 26 May 2014


COMPASSCOMPASS
Title BeiDou Performances
Edited by GMV
Level Basic
Year of Publication 2011

The BeiDou Navigation Satellite System (BDS), also known as COMPASS or BeiDou-2,[1] is China’s second-generation satellite navigation system[1][2] that will be capable of providing positioning, navigation, and timing services to users on a continuous worldwide basis[3]. The system is being deployed using an incremental approach and full operational capability is expected to be reached by 2020[3]. The BeiDou System has been designed to reach accuracy levels similar to those of GPS and Galileo Open Service: positioning accuracy within 10 meters, timing accuracy within 50 ns and velocity accuracy within 0.2 meters per second[4].

BeiDou Performances

BeiDou Navigation Test System (BeiDou-1)

The BeiDou-1 system was established in 2003, after the successful launch of BeiDou-1C satellite, for the area of the greater China and providing navigation, communication and timing services with performance characteristics as follows:[1]:

  • Positioning: 100m (1σ); 20m (1σ, with reference stations).
  • Regional Service short message service (SMS): up to 120 Chinese characters.
  • Timing: 20 ns.

BeiDou Navigation Satellite System (BeiDou-2)

The Initial Operational Service of BeiDou System was officially declared in December 2011, for which the initial performances as reported in the Munich Satellite Navigation Summit of 2012 were:

  • Service coverage area: regional
  • Positioning accuracy: 25 meters horizontally adn 30 meters vertically
  • Timing accuracy of 50 ns
  • Velocity accuracy of 0.4 m/s

These performances are being improved as the number of satellites in orbit increase and the user segment evolves.

The global BeiDou system will be built by 2020 and it is being designed to offer the following performances for each COMPASS Services[5][1][3][4][6]:

  • Open service: a free service for civilian users with positioning accuracy better than 10 meters, velocity accuracy better than 0.2 m/s and timing accuracy better than 50 nanoseconds, considering 95% probability.
  • Authorized service: a licensed service with higher accuracy even in complex situations for authorized and military users only;
  • Wide area differential positioning service: with positioning accuracy of sub-meter and meter for dual-frequency and single-frequency receivers;
  • Short message service (SMS): up to 120 Chinese characters.

Combined Services Performances

PDOP of GPS , BeiDou and combined GPS+BeiDou (elevation =7.5)[7]

Preliminary performance figures were presented in the BeiDou Workshop, integrated in the ION GNSS 2013 Conference. The BeiDou constellation available at the time already provided many visible satellites as GPS (BeiDou: 8, 9, 10, 11, 12, 13; GPS: 6, 7, 8, 9, 10, 11, 12, 13), but the values of PDOP are bigger than that of GPS (average values, BeiDou: 2.076, GPS: 1.694), as depicted in the figure[7].

The presented results shown that a combined BeiDou+GPS constellation provides[7]:

  • Higher availability: up to 15 satellites were visible in the test conditions (compared to 6 in some cases of GPS only);
  • Better geometry: the PDOP for the combined constellation was lower than the PDOP for each individual constellation;
  • Better precision: the precisions of GPS are slightly better than that of BeiDou in both horizontal and vertical direction, but the combined solution GPS+BeiDou got the best performance in all direction.


References

  1. ^ a b c d Compass/BeiDou Status, Jun Shen, BNStar Navigation Technology & System, Inc., Rome (Italy), June 11, 2009.
  2. ^ BeiDou Navigation Satellite System in Wikipedia
  3. ^ a b c BeiDou China’s Rapidly Emerging GNSS, InsideGNSS, May/June 2014
  4. ^ a b BeiDou System, Open Service Performance Standard, China Satellite Navigation Office, Version 1.0, December 2013
  5. ^ China Satellite Navigation Office, Development of BeiDou Navigation Satellite System, Munich Satellite Navigation Summit, 2011
  6. ^ Ran Chengqi: The Construction and Development of Beidou Navigation Satellite System
  7. ^ a b c The Comparison on the Positioning Performance Between BeiDou and GPS: Y. Xu, S. Ji, W. Chen, D. Weng, Y.Xu, W. Chen, D. Weng, The Hong Kong Polytechnic University, Hong Kong; S. Ji, China University of Petroleum, China, ION GNSS 2013.
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