Chief Designer of Beidou： Navigation accuracy comparable to GPS will serve the world in 2020
It has become a "national weapon" and has global service capabilities within four years
On June 12, 2016, the 23rd Beidou navigation satellite was successfully launched. Today, the Beidou navigation system’s services cover one-third of the world’s land, benefiting 4 billion population in the Asia-Pacific region, and its accuracy is comparable to GPS. Xie Jun, chief designer of the Beidou navigation satellite system, said in an interview with reporters that the Beidou satellite navigation system has endless potential, and as the Beidou system has global service capabilities in 2020, it will play a greater role in development and application. "Beidou is China’s Beidou, and it is the world’s Beidou." To some extent, it can be said that the Beidou system is the most competitive representative of China in the world’s scientific and technological competition. It is also the brand spokesperson of "Made in China".
Wen, Guangzhou Daily reporter Xiao Huanhuan
Serving the world in 2020
Reporter: What is the principle of Beidou navigation?
Xie Jun: Anyone familiar with GPS knows that satellite navigation actually determines the position information of the satellite by measuring the distance between the satellite and the ground station and determining the clock relationship between them. After knowing the position and time information of the satellite, the ground user can calculate his position after receiving the navigation signals of four satellites at the same time. This is the principle of satellite navigation and positioning.
Reporter: After the successful launch of the eighth satellite, it was possible to navigate and locate. Why did so many satellites launch later?
Xie Jun: In terms of navigation satellite constellation design, four factors are mainly considered: coverage, availability, integrity, and continuity. After the eighth Beidou navigation satellite is put into orbit, in principle, it can provide continuous and stable service capabilities to the regional area 24 hours a day. However, in order to improve the stability of the entire constellation, it is necessary to add some satellites, so that users can receive more satellite signals at the same time, and can more easily calculate their own positions. In addition, increasing the number of satellites can also improve the accuracy of navigation and positioning for end users.
Reporter: What factors does the positioning accuracy of a navigation system depend on?
Xie Jun: Positioning accuracy is the most important indicator in a navigation system. Positioning accuracy is closely related to navigation satellites, ground operation control, and user end points. Technically, there are measurement errors and clock errors in these parts, as well as ephemeris errors, atmospheric and ionospheric influences, which are all important factors affecting positioning accuracy. If these errors are corrected well, the positioning accuracy of the user machine will be high. Of course, there may be interference in the working environment of the user machine, which will also affect the positioning accuracy. There is also the geometric configuration of the satellite constellation. Good configuration is also very important to improve positioning accuracy.
Reporter: How is our Beidou navigation system "three steps" strategy progressing now?
Xie Jun: The overall idea of the design of the Beidou navigation system is to put the region first and then the world. Adopt a "three-step" development strategy. The first step is to establish a Beidou satellite dual-satellite positioning test system to form a regional active positioning and navigation service capability; the second step is to complete the launch of more than ten satellites in three orbits, build a regional navigation system, form a regional passive service capability, and provide positioning, navigation, timing, and short message communication services to the Asia-Pacific region; the third step is to build a Beidou global satellite navigation system composed of 5 geostationary orbit satellites and 30 non-geostationary orbit satellites, forming a global passive positioning service capability.
In 2012, the Beidou satellite regional navigation system ushered in a 5-star intensive launch period from the eleventh to the fifteenth. Among them, the twelfth and thirteenth satellites and the fourteenth and fifteenth satellites were all launched with one arrow and two satellites. On October 25, 2012, the sixteenth Beidou navigation satellite was successfully launched, and the Beidou satellite regional navigation system completed all satellite launch tasks. So far, the space segment of the Beidou satellite regional navigation system consists of a constellation of 14 satellites distributed in different orbits, namely 5 geostationary orbit satellites, 5 tilted geostationary orbit satellites and 4 medium orbit satellites. China has fully completed the construction of the regional navigation system, forming a service capability covering most of the Asia-Pacific region.
At present, the first two steps have been achieved, and China has become the fourth country in the world to have an independent satellite navigation and positioning system. China’s latest two Beidou navigation satellites have made a major breakthrough compared with the previous Beidou satellites. The localization rate of components has increased to 98%, and its key components such as "heart", "brain" and "iron bone" are all domestically produced. By 2020, 35 satellites will be launched and networked to provide services to global users. Beidou navigation accuracy is comparable to GPS. Reporter: You also mentioned before that our Beidou navigation system provides both active and passive positioning. This is one of our characteristics?
Xie Jun: The service provided by GPS now is called passive positioning. It means that users can receive satellite signals for free without sending any signals to achieve their own location. The Beidou system provides two services. One is the same as GPS, allowing users to directly receive satellite signals for free in the area to achieve positioning. The other is active positioning, where users can report their location to other networks or command and control centers, and finally achieve positioning. Active positioning is widely used in dispatching systems and command systems. It can achieve rapid ground positioning, and the command and dispatch of related application industries will become easier. For example, just like the dispatching room of a bus, we can immediately know your location, and we can calculate how long you have been there in the past. This kind of active positioning is a feature of Beidou, and from the perspective of the development trend of satellite navigation, it is also something we should adhere to. One of the goals of the Beidou navigation system is to build active navigation and positioning and short message functions in 2020. This is a function that is not currently available in GPS. The short message function is that the satellite positioning end point and the Beidou satellite or the Beidou ground service station can directly transmit information in two directions through satellite signals, and GPS can only be transmitted in one direction. Compared with the first-generation binary satellite system, the Beidou satellite navigation system has begun to show more characteristics and advantages.
Reporter: Why do we have more Beidou navigation system satellites than GPS?
Xie Jun: Compared to the 24 satellites owned by the US GPS system, the Beidou satellite navigation system has 11 more satellites. Because it consists of three parts: the space segment, the ground segment, and the user segment. The space segment includes 5 geostationary orbit satellites and 30 non-geostationary orbit satellites. The ground segment includes several ground stations such as the main control station, the injection station, and the monitoring station. The user segment includes the Beidou user end point and the end point compatible with other satellite navigation systems. We have more satellites than GPS because the constellation design of the two systems is different.
Beidou belongs to China and the world
Reporter: How far is Beidou navigation compared to GPS in the United States?
Xie Jun: In the field of satellite navigation, the United States is indeed one step ahead. Its GPS should have provided services in 1994. When our country officially launched the construction of the Beidou navigation system in 1994, it was almost 20 years later than the GPS navigation system. This is a huge pressure for us and a driving force. We only entered a fast lane in 2000. In 2004, we only had one channel for active positioning, so the number of users was very limited. Relative to the number of unrestricted GPS users, it is incomparable to them, and it may not even be one ten thousandth of them. By the end of 2012, we could basically cover most of the Asia-Pacific region, and we achieved this active and passive service in China and surrounding areas. We are still in a period of rapid development. Nowadays, in China or the surrounding areas of China, we are on par with GPS.
In terms of application, it should be said that it is not as good as GPS, but in terms of accuracy, it is already comparable to GPS. With our supporting ground augmentation system, it should be said that the accuracy is now meter-level, and some companies in individual industries have achieved a level better than meter-level. Of course, users who are willing to use Beidou can use Beidou, and who are willing to use GPS can use GPS. I believe that due to some characteristics of Beidou, there will be more and more users of Beidou in the end. Beidou is China’s Beidou and the world’s Beidou. Don’t worry about the elderly walking with Beidou.
The Beidou navigation system is closely related to the lives of ordinary people. The concepts of "vehicle to everything", "wearable devices" and "Internet of Things" that are currently hot in the market are all inseparable from Beidou. Taking "wearable devices" as an example, domestic companies have launched products related to the Internet of Things and wireless communication technology based on the Beidou satellite positioning system. End point provides the elderly with applications such as one-click calls, one-click emergency help, voice reminders, and wireless collection of medical data such as blood pressure and ECG. After the elderly bring the end point products, they will be connected to the intelligent service platform, and their families can keep abreast of the elderly’s location and physical condition at any time. They can also set up protective circles and voice reminders to contact healthcare workers.
In addition, Beidou has also played a role in self-driving tours, adventure tours and other tourism fields. For mountaineering enthusiasts, Beidou positioning services can ensure that they can be rescued at any time after an accident.
Reporter: Now the United States has GPS, Russia has its own satellite navigation system, and Europe has its own system. Is it necessary to have so many navigation systems?
Xie Jun: In fact, experts in the United States have also talked about this issue before. They said, do the world really need four major systems or several major systems? Each system requires more than 20 satellites to form its own independent network, so the four major systems will definitely be hundreds of navigation satellites in the future. Is there such a need? But later we found that in fact, countries have their own special requirements, but the ultimate benefit is the user. He can choose Beidou or GPS, which is very convenient and accurate. With a compatible foundation, users have more choices and more services.
Reporter: Is it safer to use our own system?
Xie Jun: We know that any system design, including the current network, has backdoors. You can use other people’s system backdoor keys to master in the hands of others. My own system should be said to be very reassuring. Before 2010, we still had to rely on foreign imports for some key components, such as some computer processing chips, some memory, and large-scale integrated circuits. But after that, some of the large components on the Beidou satellite were all developed by ourselves, such as atomic clocks, high-power amplifiers, and some precision measurement components, all of which were developed by our country’s enterprises.
Reporter: What are the advantages of the Beidou system compared to GPS?
Xie Jun: The first is compatibility and interoperability. This will bring many benefits to users, because users can receive more navigation satellite information at the same time, and it is more convenient to calculate their own position, speed, and time, and the accuracy is also higher. After the Beidou system is compatible with other systems, you can use Beidou when the Beidou signal is strong, and use GPS to help you correct it and help improve the accuracy of navigation services. As early as a few years ago, many companies have begun to try to manufacture receivers that can receive Beidou, GPS, and GLONASS systems. After the world’s four major satellite navigation systems reached a compatibility and interoperability agreement, the compatibility between systems is completely no problem.
Secondly, one of the goals of the Beidou navigation system is to build active navigation and positioning and short message functions in 2020. This is currently a function that Glonass and GPS do not have.
Reporter: What is the application prospect of the Beidou navigation system?
Xie Jun: Since the official provision of regional services on December 27, 2012, the Beidou Navigation Regional System has been operating continuously, stably and reliably, and its services cover one-third of the world’s land, benefiting 4 billion population in the Asia-Pacific region, reflecting China’s responsibility and status.
The implementation of the Beidou project has led to the development of satellite navigation, surveying, electronics, components and other technologies in our country. It has been widely used in the fields of transportation, communication, electric power, surveying and mapping, disaster prevention and relief in our country, and has driven industrial transformation and upgrading. Specific to the lives of ordinary people, it can provide continuous, stable and reliable navigation and positioning services for the surrounding areas of our country. We have many systems and many users, and it has unique functions in the field of transportation, geodetic surveying and mapping, and emergency disaster relief command and dispatch in agriculture and fisheries.
For example, everyone’s car is equipped with a standard car navigation system, which is an example of the application of satellite navigation systems. At the same time, there are some watches that indicate leisure travel, and some indicators are also realized by using our satellite navigation system. In the future, we will also build a navigation system that serves the world. It can be said that the Beidou satellite navigation system has strong strength and endless potential.