The rotation-corrected integrated POD method holds significant promise for global navigation augmentation, autonomous LEO-based navigation systems, and real-time positioning services.
Modern satellite constellations such as OneWeb, Starlink and CENTISPACE promise global communications and navigation capabilities using low-Earth orbit (LEO) constellations. However, their precise orbit determination (POD) requires dense ground station networks — costly and often limited by geopolitical or geographical constraints.
Inter-satellite links (ISLs) help reduce ground dependence but suffer from “rotational unobservability,” where the entire constellation drifts in orientation due to the lack of an absolute spatial reference. Existing fixes often require additional infrastructure or high-quality GNSS products, which increase latency and operational complexity.
Because of these challenges, a more autonomous, low-latency approach that leverages existing onboard capabilities is needed to ensure reliable, high-accuracy orbits for mega-constellations.
Wuhan University researchers have developed and validated a rotation-corrected integrated POD method that fuses ISL measurements with onboard BeiDou-3 (BDS-3) GNSS observations. Published (DOI: 10.1186/s43020-025-00175-8) in Satellite Navigationon Aug. 4, the study demonstrates how the technique simultaneously estimates the orbits of LEO and BDS-3 medium-Earth-orbit (MEO) satellites, corrects systematic rotation using BDS-3 broadcast ephemerides, and achieves centimeter-level precision.
The approach significantly reduces reliance on ground stations, making it well-suited for real-time applications in large-scale LEO constellations, the researchers said.
The team simulated a 66-satellite LEO constellation equipped with ISLs and onboard BDS-3 receivers, alongside 24 real BDS-3 MEO satellites. Two processing strategies were tested: using BDS-3 data from all LEOs, and from only a subset. In both cases, ISL and GNSS data were jointly processed to form a unified high–low constellation.
Due to internal-only measurements, the initial solutions exhibited significant systematic rotation — up to 40 cm cross-track error for LEOs and over 1 meter for MEOs.
This innovation could become a cornerstone technology for integrating LEO constellations with existing GNSS systems to enhance global navigation and timing performance.
The researchers derived rotation angles between the integrated POD coordinate frame and the BeiDou Coordinate System implied in broadcast ephemerides, then applied a Helmert transformation to correct the orbits. After correction, LEO along-track and cross-track errors dropped from 22.7 cm and 39.3 cm to 1.3 cm and 4.2 cm, respectively. MEO errors fell from over 1.2 m to about 13 cm.
Even when only 36 of 66 LEOs carried GNSS receivers, ISL connectivity propagated the correction across the constellation with minimal accuracy loss. Tests also examined the influence of predicted Earth rotation parameters and residual errors in broadcast ephemerides.
“This method tackles one of the most stubborn issues in autonomous constellation orbit determination — systematic rotation caused by the lack of absolute spatial reference,” said Kecai Jiang, corresponding author of the study. “By harnessing readily available BDS-3 broadcast ephemerides and inter-satellite measurements, we can deliver centimeter-level precision without waiting for post-processed GNSS products or building extensive ground networks. This approach is not only efficient but also scalable, paving the way for real-time, high-accuracy navigation services in future mega-constellations.”
The rotation-corrected integrated POD method holds significant promise for global navigation augmentation, autonomous LEO-based navigation systems, and real-time positioning services. By dramatically reducing reliance on ground infrastructure, it enables resilient operations in remote or geopolitically constrained regions. Its scalability makes it suitable for next-generation satellite constellations supporting broadband internet, disaster response, and precision agriculture, the researchers said.
Moreover, the ability to achieve near-uniform accuracy across all satellites — even when only part of the constellation carries GNSS receivers — lowers hardware requirements and operational costs. This innovation could become a cornerstone technology for integrating LEO constellations with existing GNSS systems to enhance global navigation and timing performance.
Four T300’s from ComNav Technology have been used as active control GNSS points on the top of Sweden’s tallest building, Karlatornet, during its construction to deliver 3D coordinates to total stations and one was used as a base station. The building is set to be complete this month.
The T300 is a receiver with radio frequency, a baseband chip built in, and a unique quantum-real-time kinematic (RTK) algorithm. It supports full constellation systems including BDS-2, BDS-3, GPS, GLONASS, Galileo, QZSS and NavIC.
The receiver is designed for demanding surveying tasks, features tilt compensation, 4G/Wi-Fi connection, 8-GB internal memory and an easy survey workflow with Android-based Survey Master Software. It is designed to make collecting accurate data easy and fast, whether done by a beginner or experienced professional surveyor, the company said.
As we begin 2023, GNSS development continues apace, as described in this issue’s annual “Directions” section by representatives of Galileo, GLONASS, and BeiDou. We plan to publish a similar update on the GPS program soon.
Galileo’s user base now stands at more than 3.5 billion, and the services it provides continue to improve and expand. Beginning early this year, free precise point positioning (PPP) corrections for Galileo and GPS (single- and multi-frequency) will improve real-time user position by up to 10 times. While the discontinuation of Soyuz launch services from the Kourou Space Centre in French Guiana, due to the Russia-Ukraine conflict, delayed the two Galileo launches that had been planned for last year, 2022 was a key year for the development of Galileo Second Generation (G2G) satellites. They will provide, among other innovations, a reconfigurable fully digital navigation payload, point-to-point connection between satellites, and advanced jamming and spoofing protection mechanisms.
On Nov. 29, 2022, Russia launched the 51st Glonass-M satellite, about 20 years after launching the first one. Currently, 13 of these satellites are operating beyond their guaranteed lifetime, with an average orbit lifetime of more than 10 years. Starting this year, the constellation will be renewed by Glonass-K and Glonass-K2 satellites, which provide CDMA signals to users.
Currently, 45 BDS satellites are operational in orbits, including 15 BDS-2 satellites and 30 BDS-3 satellites. The constellation says that it has reached a continuity of 99.996% and an availability of 99%, with a global positioning accuracy better than 1.5 meters horizontally and 2.5 meters vertically (95% confidence).
Tracy Cozzens, who has been a pillar of this magazine for 17 years, is retiring this month. We will miss her journalistic acumen, dedication to clarity and style, attention to detail, and wealth of institutional knowledge. We wish her a well-deserved retirement. At the same time, we welcome aboard Maddie Saines, our new managing editor, who is near the beginning of her career.
I am pleased to announce that Rob VanBrunt has joined GPS World’s Editorial Advisory Board. In mid-December, the board of directors of Spirent Federal Systems, a provider of PNT test solutions for the U.S. government and contractors, appointed him as the company’s president/CEO-designate, a role he will assume when the onboarding process is complete.
VanBrunt began his career at Spirent Communications in 1990 as product developer and manager, and then held posts of increasing responsibilities, moving to director and vice president roles focused on management, strategy and mergers and acquisitions. Most recently, he was executive vice president in the Office of Business Excellence. VanBrunt has a B.S. in electrical and electronics engineering from Rutgers University.
Spirent Communications is a global provider of automated test and assurance solutions for networks, cybersecurity and positioning. In July 2001, the company formed Spirent Federal Systems as a wholly owned subsidiary and U.S. proxy company. Spirent Federal markets and sells Spirent Communications’ products in North America. It also provides value-added features and ongoing customer support.
On Jan. 1, I lost my beloved mother, Maristella “Mimi” Luccio. She was 87.
In 2022, the BeiDou Navigation Satellite System (BDS) continued to improve its service performance, expand global applications, and deepen and promote international cooperation.
On Nov. 4, 2022, a white paper titled “China’s BeiDou Navigation Satellite System in the New Era” was published. The paper shows the continuous, stable and reliable operational capability of BDS, its applications achievements across the industries, international development with openness and integration, and unremitting pursuit of helping to build a community with a shared future for humanity and a better world.
System Services Performances
In orbit are 45 BDS operational satellites, including 15 BDS-2 satellites and 30 BDS-3 satellites. Figure 1 shows the number of visible BDS satellites worldwide as of BDT 06:00 on Dec. 6, 2022.
Figure 1. Number of visible BDS satellites. (Image: www.csno-tarc.cn)
BDS has reached a continuity of 99.996% and an availability of 99%. The innovative constellation involves inter-satellite links, signal system optimization, intelligent operation and maintenance, software reconstruction and upgrading of in-orbit satellites, and global test and assessment.
As measured by the International GNSS Monitoring and Assessment System (iGMAS), the BDS global positioning accuracy is less than 1.5 m horizontally and 2.5 m vertically (95% confidence) — better than the nominal service performance parameters.
So far, the measured signal power spectrum envelope of the BDS satellites remains consistent with the superior signal quality; the signal-in-space accuracy of any BDS satellite is better than 4.6 m. The time offset between BDT and UTC (NTSC) remains within 26 ns.
The BDS Coordination Framework has maintained consistency with the International Terrestrial Reference Frame 2014, and the accuracy is better than 3 cm. The orbital accuracy of the broadcast ephemeris of the BDS-3 medium Earth orbit (MEO) satellite is better than 0.5 m, and the clock offset of the broadcast ephemeris of the BDS-3 satellites is better than 5 ns.
BDS concentrates on construction of the application infrastructure and has established four major characteristic service platforms:
Short Message Communication Service
Satellite-based Augmentation System Service
Search-and-Rescue Service
Ground Based Augmentation System Service.
These platforms will expand and upgrade the applications and provide more efficient and convenient services for users.
The BDS Short Message Communication Service platform realizes the interconnection with ground mobile communication systems and networks, and integrates the BDS short message communication functionality into smartphones without the need to change the SIM card or contact number.
For the BDS Satellite-based Augmentation System Service platform, the system’s ground segment includes 30 monitoring stations and two data processing centers. The system will provide single frequency (SF) and dual-frequency multi-constellation (DFMC) services through GEO satellites. The Civil Aviation Administration of China has initiated and organized the technical testing and certification of SF service before applications.
The BDS Search-and-Rescue Service provides users with distress alert information access and distribution, as well as return link services. It is currently at the initial operational stage with sound performances. The operational status of the BDS SAR payload has been submitted to Cospas-Sarsat.
The BDS Ground-Based Augmentation System Service platform’s real-time positioning accuracy can reach 2 cm horizontally and 5 cm vertically. The post-processing accuracy can reach 2 mm horizontally and 5 mm vertically. At present, the BDS ground-based augmentation network has provided the A-BDS positioning and the BDS high-precision services for more than 1.5 billion users in more than 230 countries and regions, with services delivered 2 trillion times in total, equivalent to nearly 3 billion on average per day. BDS has provided high-precision positioning services for more than 20 million mobile phones in the country.
The BDS Applications Industry
The BDS applications industry has achieved sustainable development. In 2021, the total output of China’s satellite navigation and location-based service industry reached about 469 billion yuan (about 67.4 billion U.S. dollars), with a compound annual growth rate of more than 20%. A complete industrial chain covering chips, modules, antennas, boards, terminals and services has been established.
Industrial applications. BDS has been fully applied in various industries — including transportation, agriculture, forestry and fishery, public security, disaster mitigation and relief — and has been integrated into infrastructure such as electric power, water conservation, finance and communications.
As BDS applications fields expand, its in-depth applications have been growing as well. As of June 2022, more than 8 million BDS terminals had been installed in the transportation sector. More than 1.3 million terminals were used in the farming, forestry, livestock and fishing industries, and more than 1.8 million terminals were adopted by public security agencies. Large-scale BDS applications have been advanced in communication and timing services, meteorological monitoring, emergency response and disaster mitigation, and urban management. In emerging applications sectors, BDS has served epidemic prevention and control, telemedicine, caring for seniors, promoting the realization of intelligent health services that serve everyone, and accelerating intelligence and modernization in related fields.
Mass market applications. BDS has been widely used in mass market applications, such as mobile phones and wearable devices. In the first half of 2022, among all types of smartphones that applied for network access in China, 128 supported the BDS-based positioning function. More than 130 million smartphones supporting BDS services were shipped, accounting for more than 98% of the country’s total volume. The BDS positioning service is used more than 100 billion times daily on average for a platform that supports mobile map navigation. In particular, mobile phones have been fitted with high-precision positioning services. Lane-level navigation has been implemented in eight cities in China, including Shenzhen, Chongqing and Tianjin. The first mobile phone in the world that supports BDS-3 regional short message communication services has been officially released, enabling users to send short messages through BDS.
BDS international applications. BDS has been applied in more than half the countries and regions in the world, with more diversified application modes and application fields.
BDS products, technologies and services have been recognized by more international users:
In Mozambique, BDS-based UAVs have greatly improved the efficiency of plant protection operations
In Lebanon, BDS-based high-precision technology has been successfully applied to the construction and measurement of the port of Beirut
In Burkina Faso, BDS supported surveying and mapping during the construction of hospitals to prevent and control local infectious diseases, such as COVID-19
In Saudi Arabia, BDS is widely used in fields such as surveying and the collection of geographic information, the construction of urban and municipal infrastructure, and the positioning of personnel or vehicles in deserts
In Asia, BDS-based high-precision positioning services are contributing to the monitoring of Sarez Lake Dam in Tajikistan, the completion of the China-Kyrgyzstan-Uzbekistan Highway, the China-Kazakhstan crude oil pipeline, and the routine operation of China-Europe Railway Express.
International Cooperation
Following the principles of openness, cooperation and resource sharing, BDS has been actively carrying out practical international cooperation and exchanges as well as facilitating the development of global satellite navigation.
Multilateral cooperation. BDS representatives continue to participate in international activities under the framework of the United Nations International Committee on GNSS and other multilateral forums, to advocate joint development of global satellite navigation by contributing Chinese wisdom and proposals. BDS has also participated in international academic conferences in the field of satellite navigation, such as the Institute of Navigation meetings, the Munich Satellite Navigation Summit, and the Multi-GNSS Asia Conference.
Bilateral cooperation. The Ninth Meeting of the China-Russia Project Committee on Major Strategic Cooperation in Satellite Navigation was successfully held in September 2022. Under the framework of the Committee, BDS and GLONASS have carried out continuous cooperation in such areas as compatibility and interoperability, system performance testing and assessment, and joint applications. China’s Satellite Navigation Office signed cooperation documents in the field of satellite navigation with partners from the United Arab Emirates and the Arab Civil Aviation Organization, to carry out extensive cooperation and continue to deepen cooperation with Pakistan, Iraq, Thailand, Argentina, South Africa and other countries.
International Standards. BDS is increasingly recognized by international organizations such as the International Maritime Organization (IMO), the International Civil Aviation Organization (ICAO), Cospas-Sarsat, IEC, 3GPP and RTCM. In November 2022, the BDS Message Service System (BDMSS) was ratified by the Global Maritime Distress and Safety System (GMDSS), making BDMSS the third GMDSS satellite communication system recognized by the IMO. The Declaration of Intent for Cospas-Sarsat MEOSAR Cooperation was signed between the cooperating agencies (from Canada, France, Russia, and the United States) of the International Cospas-Sarsat Program and the Maritime Safety Administration of China, meaning China formally becomes the provider of the Cospas-Sarsat space segment.
The Future
In the future, BDS will launch back-up satellites to ensure better performance by upgrading the constellation’s availability. While maintaining stable operation, BDS will speed up in combination with new technologies such as 5G, artificial intelligence and Big Data to build a more ubiquitous, more integrated, and more intelligent national comprehensive PNT system by 2035. BDS will continuously adhere to the development concept that “BDS is developed by China, dedicated to the world and aiming to be world class,” promote system development and make contributions to social development and construction of the community with a shared future for mankind.
For analogous updates on the other three GNSS constellations, please see:
Yang Changfeng is BeiDou’s Chief Architect. (Photo: BeiDou Navigation Satellite System)
Construction of the BeiDou Navigation Satellite System (BDS-3) has been completed. The system was formally commissioned on July 31, 2020. In 2021, BDS continued to improve performance, expand applications and deepen cooperation, and has achieved sustained, stable and rapid development.
System Performance and Services
Currently, 45 BDS satellites are operational in orbit — 15 BDS-2 satellites and 30 BDS-3 satellites jointly provide seven types of services to users. Specifically, for the entire planet, the system provides three services:
Positioning, navigation and timing (PNT).
Global short-message communication.
International search-and-rescue (SAR) services.
For the Asia-Pacific region, the system provides four additional services:
Satellite-based augmentation.
Ground-based augmentation.
Precise point positioning.
Regional short-message communication services.
The system has been operating continuously and stably since commissioning, with the average value of satellite availability better than 0.99 and the average value of satellite continuity better than 0.999.
PNT Service. As actually measured by the International GNSS Monitoring and Assessment System (iGMAS), the global horizontal positioning accuracy is about 1.52 meters, the vertical positioning accuracy is about 2.64 meters (B1C signal single frequency, 95% confidence), the velocity measurement accuracy is better than 0.1 m/s, and timing accuracy is better than 20 nanoseconds. The performance is better in the Asia-Pacific region.
FIGURE 1 shows the number of visible BDS satellites worldwide at BDT 00:00 on Nov. 18, 2021. Among them, the number of visible BDS satellites exceeds 20 in some areas of the Asia-Pacific region.
Figure 1. Number of visible BDS satellites, elevation ≥5° (2021/11/18/00:00 BDT). (CREDIT: www.csno-tarc.cn)
Global Short Message Communication Service. Trial service is provided through 14 medium-Earth-orbit (MEO) satellites for authorized users and low-orbit satellites, with a maximum single-message length of 560 bits, equivalent to about 40 Chinese characters.
Search-and-Rescue Service. A COSPAS/SARSAT-compliant MEOSAR service is provided by six payloads deployed on six MEO satellites. A B2b signal-based Return Link Service (RLS) is provided through 24 MEO and three IGSO satellites, which have completed testing and verification and are in the process of coordination within the framework of COSPAS-SARSAT.
Satellite-Based Augmentation Service. China’s Civil Aviation Administration is organizing satellite-ground integrated test and evaluation, and the positioning accuracy, alarm time, integrity risk and other indicators meet the requirements.
Ground-Based Augmentation Service. Real-time centimeter-level and post-processing millimeter-level services are provided for industrial and public users, based on the regional network reference stations built in China.
Precise Point Positioning Service. PPP signals are broadcast by three GEO satellites. The measured horizontal positioning accuracy is 0.24 m, the vertical positioning accuracy is 0.41 m (95% confidence), and the convergence time is less than 20 minutes.
Regional Short Message Communication Service. The short-message communication function has been tested and verified for integration into public mobile phones; large-scale application is planned.
Development of the Applications Industry
Large-scale applications of BDS have entered a critical stage of liberalization, industrialization and internationalization. The overall output value of China’s satellite navigation and location-based service industry continued to grow in 2020, up to 403.3 billion yuan (US$63.2 billion), which is about 16.9% more than its value in 2019. In terms of BDS-3-enabled basic products, an industrial chain is gradually maturing, comprised of BDS/GNSS basic chips, modules, boards, antennas and other components.
The certification and testing system of basic BDS products has been established and implemented. BDS is already supported by most mainstream chips. BDS is increasingly being integrated into the daily life of the general public. It is becoming the standard configuration for positioning functions of smartphones and other mass-market products.
Smartphone manufacturers such as Xiaomi, Huawei, Apple and Samsung already support BDS. In the first three quarters of 2021, among all types of smartphones applying for online access in China, 72.3% supported positioning function based on BDS, accounting for 93.5% of the total sales volume. The BDS ground-based augmentation function has been introduced into smartphones to achieve high-precision positioning at the 1-meter level; lane-level navigation is being piloted in several cities in China.
In terms of industrial applications, BDS has fully served multiple industries including transportation, public security, disaster relief, agriculture, forestry, animal husbandry and fishing. It has accelerated the integration into electricity, finance, communications and other infrastructure. In particular, in the fight against COVID-19 through scientific and technological approaches, BDS-based precise positioning has facilitated the efficient supply and circulation of anti-epidemic materials.
BDS-based solutions for land rights determination, precision agriculture and smart ports have served the economic and social development of countries in Asia, Eastern Europe and Africa, and BDS-based products have been applied in more than half of the world’s countries and regions.
International Cooperation
BDS has always adhered to the development concepts of openness, cooperation and resource sharing; actively carried out practical international exchanges and cooperation; and contributed to China’s peaceful use of outer space.
Bilaterally, the Eighth Meeting of the China-Russia Project Committee on Major Strategic Cooperation in Satellite Navigation was held in October 2021. Both sides jointly formulated and signed the Roadmap for Cooperation in the Field of Satellite Navigation from 2021 to 2025, providing planning and guidance for China-Russia satellite navigation cooperation in the next five years. Also, China’s Satellite Navigation Office signed a memorandum of understanding on satellite navigation cooperation with the National Committee on Space Activities of the Republic of Argentina and the South African National Space Agency, and formally established a regular cooperation mechanism.
BDS is gradually being integrated into international standards, and is steadily promoting ratification by international standards bodies, including in the civil aviation, maritime, SAR, mobile communications and electrotechnical fields. Several international standards supporting BDS have been released. The Chinese government has drafted a letter of commitment to the International Civil Aviation Organization (ICAO), stating that BDS will provide basic services free of charge to civil aviation users around the world. The International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA) has officially issued a standard that ratifies BDSBAS, so that global marine users can carry out applications based on it. The Third Generation Partnership Project has started the standardization of BDS-3’s B2a and B3I signals. In the detection standard for Indicating Radio Beacon Locator of the Global Maritime Distress and Safety System issued by the International Electrotechnical Commission, BDS receivers and BDS-based SAR services will be supported.
The Chinese government is steadily advancing the rule of law, attaching great importance to and comprehensively promoting the rule of law for satellite navigation. A legal system on BDS has been formed, consisting of national policies, industrial and local policies and regulations, and more. The legislative process of the Satellite Navigation Regulations of the People’s Republic of China has been actively promoted to ensure the healthy, rapid and sustainable development of the satellite industry. In May 2021, China issued a development report on the rule of law of BDS.
Follow-Up Plan
In the future, on the one hand BDS will ensure stable operation, while on the other hand it will focus on the development of backup satellites, and complete the production, state optimization and ground testing of backup satellites. Backup BDS-3 satellites with better performance will be launched as needed to further improve the reliability of the constellation. By adhering to the development concept of “BDS is developed by China, dedicated to the world and aiming to be first class,” carrying forward the BDS spirit of the new era of “independent innovation, open integration, unity of all, pursuit of excellence,” BDS will serve the world and benefit all humankind.
Number of BDS-3 satellites in orbit: 30
Signals broadcast: B1I, B3I, B1C, B2a, and B2b
Yang Changfeng is chief architect of the BeiDou Navigation Satellite System and a Chinese Academy of Engineering academician.
China and the Arab states will expand their cooperation in using the China-developed BeiDou Navigation Satellite System (BDS), according to the third China-Arab States BDS Cooperation Forum and reported by XinhuaNet.
China and the Arab states will jointly implement pilot projects in key domains in the application of BDS and GNSS over the 2022-2023 period, according to a cooperation action plan signed at the forum, held Dec. 8 in Beijing.
Both sides will facilitate the establishment of BDS/GNSS centers in the Arab states, hold training courses on satellite navigation technologies, and exchange visiting scholars. Each year, China will offer scholarships to three to five students majoring in navigation and communications from the Arab states, said the action plan.
China and the Arab states will also carry out joint BDS/GNSS tests and evaluations, and promote the application of BDS in international search and rescue, among other initiatives.
All the moves are expected to boost “win-win cooperation” and make BDS better serve the Arab states, said the action plan.
This year’s forum was held after China officially commissioned BDS on July 31, 2020, opening the new BDS-3 system to global users.
Along with positioning, navigation and timing services, the BDS-3 system can provide a variety of value-added services such as global search-and-rescue assistance, short message communication, ground- and satellite-based augmentation, and precise point positioning.
The forum highlighted the achievements and experience of China and Arab states in BDS/GNSS cooperation and proposed a platform for both sides to upgrade the win-win cooperation.
BeiDou benefits in Arab States
The BDS-based applications and solutions have benefited multiple industries in Arab states. BDS has been providing real-time, continuous, stable and precise GNSS positioning information data and timely information via continuously operating reference stations (CORS) in Tunisia, Algeria and other places.
High-precision BDS/GNSS applications are also serving diverse fields such as land mapping, transportation, precision agriculture and environmental monitoring.
Project management of railway construction in the United Arab Emirates (UAE) has benefitted from the integrated technologies of BDS/GNSS and the internet of things, with efficient use of data and information.
BDS has entered a new phase of industrial and international development, according to the China Satellite Navigation Office.
Yang Changfeng, chief architect, BeiDou Navigation Satellite System, speaks at an international event. (Photo: BDS)
On July 31, 2020, BDS-3, the global version of the BeiDou Navigation Satellite System (BDS), was formally commissioned, marking the completion of its three-step development process. BDS enters a new era of global services. With the principle of “serving the world and benefiting mankind,” BDS provides seven types of services to users worldwide, including positioning, navigation and timing (PNT) services, a global short-message communication (GSMC) service, a regional short-message communication (RSMC) service, an international search-and-rescue (SAR) service, the BeiDou satellite-based augmentation system (BDSBAS), the BDS/GNSS ground-based augmentation system (BDGAS), and the precise point positioning (PPP) service. BDS has been continuously making contributions to improving GNSS capabilities and promoting the development of GNSS applications and technologies.
In 2020, as BDS construction was successfully completed, BDS has made fruitful achievements in application development and internationalization.
System Construction
Space Constellation Deployment. From March to June 2020, two BDS-3 GEO satellites were launched, while the in-orbit tests of two IGSO satellites, two GEO satellites, and two MEO satellites were completed. As the result, the global system constellation was successfully deployed.
By the end of October 2020, 45 in-orbit operational BDS satellites provide services to global users, including 15 BDS-2 satellites and 30 BDS-3 satellites.
Ground System Development. More than 40 new ground stations have been built, tested and commissioned. The BDS ground system is operating stably, supporting daily BDS operations.
Basic Service Enhancement
Generally speaking, the accuracy of the BDS signal-in-space is better than 0.5 m, BDS global positioning accuracy is better than 10 m, BDS velocity measurement accuracy is better than 0.2 m/s, and BDS timing accuracy is better than 20 ns. In the Asia-Pacific region, BDS positioning accuracy is better than 5 m, the velocity measurement accuracy is better than 0.1m/s, and timing accuracy is better than 10 ns.
In the key service area, there are 30 BDS-3 satellites and 15 BDS-2 satellites that jointly provide the services using B1I and B3I signals. The actual average measured positioning accuracies are about 1.48 m horizontally and 2.99 m vertically (95% confidence), which are improvements of about 30% and 5% respectively as opposed to solely relying on the BDS-2 system.
Globally, with the B1I, B3I, B1C and B2a signals, BDS-3 offers service availability of 100% (PDOP ≤6,). The actual measured positioning accuracies are about 1.54 m horizontally and 2.65 m vertically (95% confidence).
Featured Services Benefit Users
Presently, the BDS PPP service covers China and its surrounding areas. By broadcasting the high-precision orbit and satellite clock error corrections through the B2b signal, the high-precision positioning service is provided, while initial testing measurements show that the positioning accuracies are about 0.18 m horizontally and 0.26 m vertically (95% confidence).
BDSBAS was developed in accordance with International Civil Aviation Organization (ICAO) standards to provide SBAS services with superior accuracy and integrity, enabling aircraft approach with vertical guidance of class I (APV-I). The BDSBAS services cover China and its surrounding areas, and the SBAS data, following ICAO standards are broadcast by the three BDS GEO satellites. In particular, the single frequency SBAS service is being provided through the BDSBAS-B1C signal. At the moment, the civil aviation certification process of the BDSBAS SF service is being prepared. The BDSBAS-B2a signal will provide the Dual Frequency Multiple Constellation (DFMC) SBAS service. BDS has been actively participating in the development process of the DFMC standards and carrying out the verification of the draft DFMC SBAS Standard and Recommended Practices.
BDGAS consists of 155 framework reference stations and nearly 2,200 regional stations in China. The system carries out high-precision applications in many fields, such as surveying and mapping, land resources, earthquake monitoring, transportation and meteorology. Its basic services include real-time positioning at the meter, decimeter and centimeter levels, as well as precise post-processing positioning at the millimeter level.
Being developed in accordance with Cospas-Sarsat standards, the BDS MEO-SAR service provides the detection probability of the international search-and-rescue service of better than 99%, with the characteristic return link capability. In July, a joint test was carried out using the BDS MEO-SAR satellites with the Cospas-Sarsat ground station in Maryland, U.S., and the relevant technical documents and the equipment admittance testing reports were formally submitted to Cospas-Sarsat, which provides Chinese contributions to the international MEO-SAR family.
RSMC provides service to China and its surrounding areas through three GEO satellites. Its communication capability is greatly improved compared to BDS-2. With service capacity of 12 million times per hour, the transmitting power of user terminals is reduced to 1-3 W and the single message capacity reaches 1,000 Chinese characters. The construction of the RSMC service platform has been completed to promote the organic integration of short message and mobile communication services, and to further exert the advantages of the BDS featured services.
GSMC provides global services through 14 MEO satellites with single message capacity of 40 Chinese characters.
Figure 1. The number of visible BDS satellites as of BDT 13:00, Oct. 29, 2020. The number of visible satellites at Asia-Pacific Region is greater than 20. (Source: www.csno-tarc.cn)
Integrated Applications
As the system construction accelerates, BDS is also making great efforts to strengthen the development of BDS fundamental products and promote large-scale applications in various fields. The integrated applications and innovative development adopt the “BDS+” and “+BDS” models to improve quality and efficiency as well as to stimulate a healthy and fast-growing GNSS industry.
Fundamental Products. At present, the fundamental BDS products have been used in areas such as mass-market applications, where the performance has reached or is close to the world-class level. Progress has been made in the research and development of multi-system baseband-RF integrated high-precision chips. The 28 nm chips have been mass-produced, and the 22 nm chips are about to be mass-produced. As a result, the function and performance of the chips will reach a new level. The BDS navigation chips, modules, high-precision boards and antennas have been exported to more than 120 countries and regions, serving millions of users worldwide.
Industrial Applications. BDS has been widely used in various fields, including communication and transportation, public security, agriculture, forestry, animal husbandry and fishery, hydrological monitoring, meteorological forecasting, time synchronization, power dispatching, and disaster prevention and mitigation. Significant economic and social benefits have been generated.
In the field of transportation, in the first three quarters of 2020, more than 7 million road vehicles were using BDS. The number of postal and express delivery vehicles using BDS reached 314,000, and the number of ships is about 1,369. In general aviation, 300 planes are using BDS.
In agriculture, BDS-based automatic steering systems are on more than 45,000 pieces of agricultural machinery and equipment, saving 50% of the labor cost. BDS-based agricultural machinery operation supervision platforms are serving 10 million units of agricultural machinery equipment, greatly improving management and operational efficiency.
In forestry, the BDS positioning and short message communication services are widely used in forest fire prevention, natural forest protection, forest inspection, pest control and so on.
In the fishery field, BDS provides fishery managers and fishing vessels with ship position monitoring, emergency rescue, information dissemination, vessel management and other services. BDS terminals have been installed on more than 70,000 fishing boats and law enforcement vessels in China. More than 10,000 people have been saved.
For disaster prevention and mitigation, a three-level platform covering the national ministries and the provinces was built to offer six-tier application services, deploying more than 45,000 BDS terminals.
BDS plays an important role in the emergency response to major disasters such as flooding in South China and forest fire in Southwest China this year. BDS is accelerating entry into new infrastructural construction, and is deeply integrated with new technologies such as next-generation communication, blockchain, the internet of things, artificial intelligence, and more. New modes, formats and markets for BDS applications are constantly emerging.
Mass-Market Applications. BDS-based navigation and positioning services have been adopted by various enterprises in the fields of e-commerce, smart mobile terminals, location-based services, the sharing economy and people’s livelihood, profoundly changing people’s production and lifestyles. Just like water and electricity, BDS provides public services that are easily accessible and available on demand. In smartphone applications, domestic and international mainstream chip manufacturers have released communication-navigation integrated chips compatible with BDS. More than 90% of mobile-phone companies applying for access to China’s domestic network support BDS positioning. Smartphones from Huawei, MI, Apple, VIVO, OPPS and other big brands in China are BDS-enabled.
BDS Standards. The updating and upgrading of the BDS standard system is progressing smoothly, with Version 2.0 to be released soon. The BDS application standard systems will be published in electric, railway and other industries. The revision of the national BDS standards is advancing steadily. Four national standards were issued in early 2019, and 28 national standards will be released by the end of 2020. Forty-two standards related to the BDS program have been issued in three batches, while 58 new standards are being formulated.
The work related to BDS intellectual properties is being carried out, and various innovation entities continue to improve BDS’ intellectual property creation, utilization and protection capabilities. Statistics shows that Chinese GNSS-related patent applications reached 12,170 in 2019 and 9,411 by the end of October, with an average growth rate of 21.7% in the past three years.
International Cooperation
Bilateral Cooperation. BDS continues to carry out bilateral cooperation with other GNSS to promote compatibility, interoperability and joint applications. Under the China-U.S. civil GNSS cooperation platform, working groups have been set up to continuously engage in cooperation and exchanges in areas such as compatibility and interoperability, augmentation systems and aviation applications, civil service provisions, etc. China and the Russian Federation held their seventh bilateral meeting in October, and have been pushing forward landmark demonstration projects such as joint ground station set-up, cross-border transportation and precision agriculture. China and the European Union are carrying out coordination, exchanges and cooperation under the framework of the China-EU space cooperation dialogue.
Multilateral Cooperation. The BDS team participates in meetings of the International Committee on Global Navigation Systems (ICG), and continuously promotes discussions on relevant topics. The experience fighting COVID-19 using BDS/GNSS, as well as BDS applications in pandemic prevention and control, are being shared with the international GNSS community. During the ninth ministerial meeting of the China-Arab States Cooperation Forum held in July, video conferences promoted the deepening of China-Arab satellite navigation cooperation.
International BDS Applications. With the export of BDS high-precision products, BDS is widely used in different regions and fields, such as land registration, precision agriculture, warehouse logistics in ASEAN countries, construction in Western Asia, airport timing and plying the seas in South Asia, power plant inspections in Eastern Europe, and land surveys in African countries. BDS high-precision products are exported to more than 120 countries and regions. BDGAS technologies and products are systematically exported, serving more than 100 million users worldwide.
International Standards. BDS has been adopted by many international organizations including the ICAO, the International Maritime Organization, Cospas-Sarsat and mobile communication. A number of international standards supporting BDS have been released. In March, the International Electrotechnical Commission (IEC) officially issued the first international standard for BDS vessel receiving equipment inspection (IEC 61108-5), which provides the basis for global classification societies to carry out type certification of BDS equipment on vessels. In July, the first batch of 3GPP standards supporting the BDS B1C signal was officially released. The series of standards will support BDS signals in Assisted GNSS (A-GNSS) of 5G communication. By year’s end, the Radio Technical Commission for Maritime Services (RTCM) 10403.X standard, which fully supports BDS, will be officially released, marking an important milestone in the creation of a general data format standard for BDS receivers.
Adhering to the development concept of “the Chinese BDS, the World’s BDS and the First Class BDS,” BDS development vigorously carries forward the Beidou spirit in the new era — independent innovation, open integration, unity and pursuit of excellence. By 2035, a more ubiquitous, integrated and comprehensive national PNT system with a spatial-temporal information service infrastructure covering space, sky, Earth and sea, and offering unified high precision, high intelligence, high security and high efficiency, will be built. It will provide core support for future intelligent and unmanned development; continuously promote system upgrading; integrate new technologies such as new generation communication and low orbit augmentation; strive to develop high-quality capabilities such as quantum navigation, full-source navigation, and micro PNT; and build a spatial-time information service infrastructure covering space, sky, Earth and sea, with high precision, high intelligence, high security and high efficiency.
China completed its worldwide BeiDou navigation satellite system with the launch of its final satellite on June 23, according to China Global Television Network.
The satellite launched aboard a Long March-3B carrier rocket from the Xichang Satellite Launch Center at 9:43 a.m. Beijing time (0143 GMT) on Tuesday, marking the completion of the country’s domestically developed BeiDou constellation.
The launch followed a delay of after originally being scheduled for July 16 because of a technical issue discovered in pre-flight tests.
The final satellite is a geostationary earth orbit satellite of the BDS-3 system. It is the 30th BDS-3 satellite and the 55th BeiDou satellite. BDS-3 is a a 30-satellite navigation system.
BDS-3 offers high-precision positioning and short message communication.
Begun in 1994, BDS-1 was completed in 2000 to provide services to China. In 02012, BDS-2 was finished, and has provided navigation service to the Asia-Pacific region. Once the final satellite achieves orbit and is checked out successfully, BDS-3 will provide navigation services worldwide.
The 45th satellite of the BeiDou Navigation Satellite System — launched on May 17, 2019 — has started operation in the network after completing in-orbit tests, reports China’s Xinhua news service.
The satellite will provide services in place of the third BeiDou satellite, a geostationary earth orbit satellite of the BDS-2 system, according to China’s Satellite Navigation System Management Office.
The replacement will help reinforce the BDS-2 system and support a smooth transition from the BDS-2 system to the BDS-3 system. The third satellite — launched Jan. 17, 2010 — will stay in orbit after the replacement.
Yang Changfeng, Chief Architect, BeiDou Navigation Satellite System. (Photo: BeiDou)
By Yang Changfeng Chief Architect, BeiDou Navigation Satellite System
As one of the core Global Navigation Satellite Systems (GNSS) providers, the BeiDou Navigation Satellite System (“BDS”) has been developed steadily following a three-step strategy. BDS has been providing global services since the end of 2018. By around 2020, the BDS-3 system will be entirely completed to provide global users with free, open and high-quality navigation, positioning, timing, short message communication and other services. A more ubiquitous, integrated and intelligent positioning, navigation, timing system will be built before 2035.
In 2019, BDS has progressed with regard to aspects of system construction, integrated applications and international development.
System Construction
Accelerating Satellite Deployment. From January to November 2019, three BDS-3 satellites in inclined geosynchronous satellite orbit (IGSO) and four satellites in medium Earth orbit (MEO) were launched, and one IGSO satellite has completed in-orbit tests, to further improve the global system constellation.
The last two MEO satellites are planned to be launched by the end of 2019, marking the completion of the BDS core global constellation deployment. By June 2020, another two GEO satellites will be launched, and the full deployment of the BDS-3 system will be completed.
Ground System Construction. In 2019, 12 new ground operation and control stations (including one uplink station and 11 class-II monitoring stations) have been built, to complete the satellite-ground joint debug and integration tests, and the overall operation of the system is stable.
By the end of October 2019, 34 BDS satellites are operating in orbit to provide services to global users, including 15 BDS-2 satellites and 19 BDS-3 satellites.
Improving Service Performance
Key Service Areas. In May 2019, the last BDS-2 backup satellite was launched to further improve the performance in the key service areas of the BDS-2 system. As the BDS-3 satellites go into operation, the accuracy and availability of the BDS B1I and B3I signals, in the BDS-2service area, has been improved by about 30% and 5% respectively, compared with that of solely relying on the BDS-2 system.
Global Service Areas. The BDS B1I and B3I service areas have been expanded from the Asia Pacific region to the world, and the accuracy and availability have been further improved. With the condition of PDOP ≤6, the availability is better than 99% in most regions all over the world (in parts of the United States, better than 97%). In the global area, the mean value of the actual measured positioning accuracy is about 3.6m horizontally and 6.6m vertically, velocity measurement accuracy is about 0.05m/s, and timing accuracy is about 9.8 nanoseconds (95% confidence). So far, the BDS-3 new signals, B1C and B2a, have possessed service capacity worldwide. The system availability is better than 87%, in the condition of PDOP ≤ 6. The mean value of the actual measured positioning accuracy is about 2.4m horizontally and 4.3m vertically, velocity measurement accuracy is about 0.06m/s and timing accuracy is about 19.9 nanoseconds (95% confidence).
Building of the Featured Capacity. The BDS/GNSS ground based augmentation system has been providing basic services. It consists of 155 framework reference stations and nearly 2,200 regional stations in China. The system has carried out high-precision applications in many fields, such as surveying and mapping, land resources, earthquake, transportation and meteorology. Its basic services include real-time positioning at the meter, decimeter and centimeter level, as well as precise post-processing positioning at the millimeter level.
The BeiDou Satellite-Based Augmentation System (BDSBAS) is being developed in accordance with International Civil Aviation Organization (ICAO) standards to provide navigation services with superior accuracy and integrity. In 2019, the first GEO satellite with the BDSBAS payload has been tested in orbit and the satellite is in good condition.
Integrated Applications
As the system construction accelerates, BDS is also making great efforts to strengthen the development of the fundamental products and applications in various fields. The integrated applications adopt the “BDS+” model to stimulate the growth of satellite navigation industry.
Fundamental Products. At present, the fundamental BDS products have been used in such areas as mass market applications, of which the performance has reached or is close-to the world-class level. The development of full-frequency integrated high-precision chips is near its completion, and the performance of the BDS chips will improve further. By the end of 2019, BDS navigation chips, modules and antennas have been exported to more than 100 countries and regions. In 2018, the domestic output value was more than RMB 300 billion (US$43 billion), in which the BDS contribution exceeds 80%.
Industrial Applications. BDS has been widely used in various fields — communication and transportation, public security, agriculture, forestry, animal husbandry and fishery, hydrological monitoring, meteorological forecast, time synchronization, power dispatching, disaster prevention and mitigation — generating significant economic and social benefits. In the field of transportation, by September 2019, more than 6.47 million road operating vehicles and 42,300 postal and express delivery vehicles in China are using BDS, and the world’s largest dynamic supervision system of operating vehicles has been formed, which effectively improved management efficiency and road transportation safety.
In agriculture, a BDS-based automatic driving system has been equipped on more than 20,000 sets of agricultural machinery and equipment, saving 50% of the labor cost. The BDS-based agricultural machinery operation supervision platform and the IoT platform has been serving 10 million units of agricultural machinery equipment, greatly improving management and operational efficiency.
In disaster prevention and mitigation, a tri-level platform covering the national ministry, the provinces, and cities and counties has been built to offer six-tier application services, with more than 45,000 terminals using BDS. The BDS/GNSS high-precision technologies have been applied in the field of geological disaster monitoring, while the landslides in Gansu province have been successfully forecast repeatedly, with time accuracy at the second level and deformation accuracy at the millimeter level.
Mass Market Applications. The BDS-based navigation and positioning services have been adopted by various enterprises in the fields of e-commerce, smart mobile terminal manufacture, location-based services (LBS), the sharing economy and the mass market, thereby changing people’s production and life style profoundly. Mainstream manufacturers in China and around the world have introduced BDS-compatible chips that integrate communication and navigation functions.
According to Chinese market statistics, in the third quarter of 2019, 151 types of mobile phones applying for license have positioning functions, among which 110 models support BDS. Using BDS/GNSS ground based augmentation stations, the spatial-temporal services including centimeter-level positioning, millimeter-level perception and nanometer-level timing services can be provided, while the accelerated positioning services cover 220 countries and regions with more than 390 million global users.
International Development
Bilateral Cooperation. BDS continues to carry out bilateral cooperation with other navigation satellite systems, to promote compatibility and joint applications. China and the United States have set up joint working groups in areas such as compatibility and interoperability, augmentation systems and civil services to continuously develop cooperation and exchanges.
China and the EU set up a technical working group on the compatibility and interoperability between the BDS and Galileo systems to carry out coordination, exchanges and cooperation, under the framework of the China-EU space cooperation dialogue and the International Telecommunications Union (ITU). The agreement between the Government of the People’s Republic of China and the Government of the Russian Federation on Cooperation in the Field of the Use of BeiDou and GLONASS for Peaceful Purposes has come into effect.
In August 2019, China and the Russian Federation held their sixth bilateral meeting in Kazan, Russia, signed the site survey certificate of GNSS monitoring stations, and achieved many cooperation results. In addition, the bilateral cooperation with Iraq, Tunisia and Saudi Arabia has also been steadily promoted.
Multilateral Cooperation. During the 62nd session of the Committee on the Peaceful Uses of Outer Space (COPUOS) in June 2019, an exhibition on ancient Chinese navigation technologies was held at the Vienna International Center with the theme “From Compass to BeiDou,” which vividly demonstrated China’s brilliant achievements in timing, mapping, cartography and navigation science and technology. In April and October, 2019, the second China-Arab States BDS Cooperation Forum and China-Central Asia BDS cooperation forum were held in Tunis and Nanning, China, respectively, to promote the BDS to serve the Arab region and Central Asian countries.
The BDS Overseas Applications Were Steadily Promoted. With BDS high-precision products being exported, BDS has been widely used in different regions and fields, such as land registration, precision agriculture, warehouse logistics in ASEAN countries, construction in Western Asia, airport timing and piling at seas in South Asia, electric power inspection in Eastern Europe, and land survey in African countries. As BDS-3 system continues to improve construction, it will provide quality services for more people in a wider area.
Ratification of BDS by International Standards. BDS has made a clear schedule to be ratified by the ICAO standards in 2020. It has formulated 26 standards in the field of international mobile communication based on the BDS B1I signal, and other standards based on the B1C and B2a signals are being developed. A receiver positioning result output protocol (NMEA0183) and a receiver data exchange format (RINEX 3.04) supporting BDS are to be released. Technical parameters and index information of BDS search and rescue (SAR) payloads are included in relevant COSPAS-SARSAT documents, and the development and in-orbit test of the first batch of SAR payload has been completed. The first BDS standard in the International Electrotechnical Commission (IEC) has been developed and approved and is expected to be released in June 2020.
Future Plans
After BDS achieves global service capabilities by 2020, it will further improve global navigation, positioning, timing and regional short-message communication services, and finalize global short-message communication, international search and rescue, satellite-based augmentation, precise point positioning, and other service capabilities. China’s BDS will contribute Chinese solutions to the world, and give full play of its role, with a renewed attitude, stronger capabilities and better services, to serve the world and benefit humankind.
China sent a new satellite of the BeiDou Navigation Satellite System (BDS) into space from the Xichang Satellite Launch Center in Sichuan Province at 17:43:04.482 UTC on Nov. 5.
Launched on a Long March-3B carrier rocket, it is the 49th satellite of the BDS satellite family and the 24th satellite of the BDS-3 system.
It also marked that a total of three BDS-3 satellites have been sent into the inclined geosynchronous Earth orbit.
The launch was the 317th mission for the Long March series of carrier rockets.
The new satellites and the carrier rocket were developed by the China Academy of Space Technology and the China Academy of Launch Vehicle Technology, under the China Aerospace Science and Technology Corporation.
China will launch another six BDS-3 satellites to complete the BDS global network.
A new BeiDou satellite is launched from the Xichang Satellite Launch Center in southwest China’s Sichuan Province on Nov. 5. (Photo: Liu Xu/Xinhua)
Trimble has added capabilities to its real-time network (RTN) portfolio, including the Trimble Pivot Platform and the Trimble Alloy GNSS reference receiver.
The new capabilities will enable operators to continue to meet the ongoing demand from surveyors, mapping professionals and precision farmers for accurate, reliable corrections derived from real-time networks.
The announcement was made at Intergeo 2019, the world’s largest conference on geodesy, geoinformatics and land management, taking place Sept. 17-19 in Stuttgart, Germany.
Boosting RTN performance. A well-established network software, the Pivot Platform manages and controls small, mid-size and countrywide GNSS networks. By applying sophisticated atmospheric models to reduce systematic errors, highly accurate GNSS corrections are generated and made available for a wide range of field applications.
BDS-3 now supported
Both Pivot and Alloy now access BeiDou Generation III (BDS-3) signals.
Trimble Pivot version 4.3 has been enhanced to track and store BDS-3 — RTN operators worldwide now have the ability to provide their customers with additional satellite signals to offer even more robust and reliable positioning for their applications. This update also includes a simplified Chinese user interface, providing easy-to-use software operations for Chinese RTN operators.
Released in 2018, the Alloy GNSS reference receiver was designed with the processing power needed to deliver high-quality data from multiple GNSS constellations. Alloy version 5.42 firmware tracks all available and planned GPS Block IIIA L1C and BDS-3 signals, empowering operators with a full GNSS constellation dataset.
“These updates keep the Trimble Pivot Platform and Alloy on a future driven path,” said Mark Richter, strategic marketing director, Real-Time Networks and Services portfolio for Trimble’s Advanced Positioning Division. “Our focus is to continue to deliver enhancements influenced by market demands and advancements in technology, which deliver next-generation RTN hardware and software to our customers.”
The Trimble Pivot Platform and Trimble Alloy GNSS reference receiver updates work in conjunction to provide quality GNSS corrections to network operators and end users.
Trimble real-time networks and services
Trimble RTN networks and services are a widely used GNSS infrastructure solution. Spanning a variety of applications and industries worldwide, Trimble’s hardware is specifically developed for RTN real-world environments while the software integrates seamlessly into the RTN solution for exceptional real-time performance.
The flexibility of Trimble’s solution enables users to collect, manage and analyze complex information faster and easier, improving productivity and efficiency.
