BeiDou Performances

COMPASS
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, 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. The system is being deployed using an incremental approach and full operational capability is expected to be reached by 2020. 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.

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::

• 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:

• 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)

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.

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

• 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.