The combined positioning is introduced, focusing on the modernization plan and accuracy improvement of satellite positioning technology.
In the 21st century, mankind will enter the era of space development, and space technology will profoundly affect all aspects of social life. Artificial earth satellites are an important means of space exploration and space science research. The use of satellite technology can greatly expand the acquisition and use of earth information. The current satellite positioning technology is developing rapidly. For example, the GPS of the US Department of Defense has been used for navigation of various vehicles, geodesy, surface feature and terrain information acquisition, traffic management, disaster monitoring, atmospheric monitoring, and earth plate movement. Many aspects have had an important impact; Russia ’s GLONASS has also been put into operation. The 1998 international test IGEX was obtained. However, because the GPS that plays a decisive role in the GNSS-1 system is controlled by the US military, its availability cannot be guaranteed. In order to get rid of this unfavorable situation, Europe proposed the GALILEO plan, planning to establish a new generation of global navigation satellite system GNSS-2, which is a global cooperation between government and private development and utilization management. On October 31, 2014, the "Long March 3A" carrier rocket was used to launch the first "Beidou Navigation Test Satellite" developed by China into a predetermined orbit at the Xichang Satellite Launch Center. On December 21, it launched the second Chinese satellite. "Beidou Navigation Test Satellite", together with the first "Beidou Navigation Test Satellite" launched on October 31, constitutes the "Beidou Navigation Satellite" 'The system' indicates that China has the first-generation satellite navigation and positioning system independently developed to build a perfect navigation satellite system consisting of dozens of satellites. The investment is huge, and fully utilize the satellite systems of other countries and organizations to strengthen China's satellite positioning. The system, at the same time, can also perform important basic functions in an emergency. It is a realistic development idea. Therefore, the use of different satellite systems for combined measurement and other services is of great significance to China. In the next 10 years, the United States ’ The GPS system will implement a modernization improvement plan. One is to increase the number of satellites in orbit to 30 and launch a new type of satellite GPSBlockliF. The second is to add a third carrier L5. The third is to add a C / A code on the "Fourth. Civil code and Military code separation, will be updated to the second-generation global navigation satellite system in 2010, which is very close to the European GALILEO plan. The single-point positioning accuracy of the second-generation global navigation satellite system will reach 2m, which can achieve full-week ambiguity. Real-time solution, using special algorithms for data processing, the baseline accuracy of its precision measurement will be able to reach sub-millimeter level. GLON ASS reached full operational capability in 1995, and the number of working satellites reached 25. However, due to the limitations of the Russian economic situation, too few satellites have been launched since then, and the satellites have a short life span (about 3 years). Currently only 6 The satellites are working normally. The last satellite launch was on October 13, 2000. GLONASS provided free services for global users with location and time information. On February 18, 1999, the Russian President announced an international cooperation intention on GLONASS, which means GLONASS, which was established separately, was pushed to the stage of international cooperation, which greatly enhanced the confidence of all countries in the world in GLONASS, maintained international stability, and expanded the scientific and technological cooperation relationship. Therefore, GPS and GLONASS and other satellite systems The combined system has very good development prospects.
Continuity (continuity) is the most important four factors for the successful application of satellite positioning systems in deformation monitoring, national defense, aircraft precision approach, train system scheduling and management, etc. The difference between measurement and navigation will be further reduced. As a high-precision navigation, the role of data processing will be further enhanced. In order to meet the requirements of ultra-high-precision deformation monitoring, it is necessary to analyze from the aspects of raw data collection, baseline solution, various system error characteristics, special constraints, etc. Excellent mathematical model, using efficient algorithms to achieve fast and high-precision solutions.
With the continuous development of GPS positioning theory and technology, a variety of positioning operation modes have emerged, mainly including: absolute positioning (absolute positioning), static relative positioning (static positioning), differential relative positioning (differential positioning), pseudo dynamic relative positioning (poseudokinematicpositioning), Rapid static relative positioning (rapidstaticpositioning), real-time dynamic relative positioning (RTK), network RTK Among them, network RTK is a development hot spot now and in the future. For high-precision measurement, static relative positioning, fast static relative positioning, and real-time dynamic relative positioning are mainly used. These three positioning methods all use carrier phase observations. Cycle slip is not only the main factor affecting the quality of carrier phase observations, but also inevitable. Therefore, the research on the detection and repair algorithm of cycle slip is of great significance for purifying observations, and is also the difficulty of preprocessing satellite observations. Another closely related to high-precision satellite measurement is the fast and correct solution of the whole-period ambiguity. For real-time dynamic relative positioning, it is required to quickly obtain a fixed baseline solution. The fast solution method of the whole-period ambiguity must be used for the combined measurement of GPS and GLONASS, The carrier frequencies of the two satellite systems are different, and each satellite of GLONASS uses a varying carrier frequency, which makes it more difficult to solve the ambiguity of the whole week. This is the key GPS service for multi-satellite system joint data processing. There are two standards for different users: standard services (SPS), can only get C / A code service, general users can get; precision service (PPS), only limited to licensed users. Navigation and positioning are usually carried out with pseudoranges. The accuracy of single-point positioning when SA is activated is 100m. 4:05 (UTC time) on May 2, 2000. The source of the human project is funded by the Wuhan University Science and Technology Development Fund.
In order to terminate the SA interference introduced into the GPS system, the main point of the GPS single-point PDD is to ensure military services in the combat zone and prevent the accuracy of the GPS position from being greatly improved. Relevant tests show that the single-point positioning accuracy has been improved by about 10 times, and the standard positioning accuracy before and after SA cancellation is shown in Table 1 (Michael Shawetal-, 2000). Table 1 Comparison of error terms before and after SA cancellation. Typical error of standard positioning distance / m Including SA influences Ionospheric delay, tropospheric delay clock and ephemeris error receiver noise, multipath total user equivalent ranging error, typical HDOP 95% confidence level, horizontal accuracy after the cancellation of SA. The US GPS policy published in 1996 ( The President decided to move PDD-Presideritial Decisiori Directive), emphasizing that the GPS system will be more widely used in civil, commercial, and scientific research in the United States and around the world. The GPS Affairs Bureau (IGEB) jointly managed by the Department of Defense and the Department of Transportation The blueprint for further development planning. The first meeting of IGEB was held in 1997. The central topic was to increase GPS civilian signals, thereby improving the GPS status for civil and commercial purposes. The result of the meeting was that IGEB agreed to select a second civilian frequency within 1 year After the combination of the initial plans, an RD (Operational Requirements Document) for updating GPS operation requirements was formed, which laid the foundation for the current GPS modernization plan. In 1998, Vice President Gore announced that it would add a second civilian code signal to L2. Currently only the P (Y) code is modulated on L2, which can only be used by the US military and other licensed users. Vice President Gore also stated that the third signal designed specifically for life-critical civilian purposes will begin broadcasting on satellites in 2005.
After a lot of work from IGEB, the third civilian signal called L5 was determined to be an improved signal structure of 1176.45MHz in January 1999. For example, the improved signal structure diagram adds second and third to the real-time GPS users with standard positioning. After civilian signals, redundant observation data will be generated, which can improve accuracy, improve signal availability and integrity, and enhance service continuity. For high-precision deformation monitoring, aircraft precision approach, precision agriculture, machinery control, measurement and Geoscience research and other civil purposes bring benefits. The 1996 GPSPDD and subsequent conferences also promised the US government and the Department of Defense to provide high-precision positioning services, and recommended research to prevent malicious use of GPS countermeasures, thereby ensuring that the United States and its allies Malicious use that interferes with the use of civilian GPS; to ensure civilian service outside the combat zone.
To this end, military services must have the ability to select or cancel GPS signals by region. This will be done by putting together. The frequency band is subdivided, the center band is used for C / A codes, and the edge band is used for military codes (called M codes). For its structure, see the new military code. It will have better confidentiality and adopt local broadcast. The strength can be enhanced as needed, and it can be enhanced by 20dB compared to the existing P (Y) code. The US military GPS service is further strengthened. From Table 1, it can be seen that after the SA is cancelled, the ionospheric delay becomes the largest error. Since the P code of L can be directly received, the combination of L and L2 can use a certain mathematical method to obtain the effect of the ionosphere, thereby eliminating the effect of the ionosphere in the observations. However, for civilian users, the P code cannot be directly received. Other measures are needed to reduce the impact of the ionosphere. One method is to use the ionospheric model, and the other method is to use special signal receiving technology to obtain part of the information in the encrypted Y code to achieve the purpose of calculating the ionospheric delay. The first method, due to the complexity and instability of the atmospheric structure, can only eliminate 60% of the effects of the ionosphere; the second method requires a higher L2 signal-to-noise ratio than the licensed user ’s dual-frequency receiver ( SNR) For static measurement, a high signal-to-noise ratio can be obtained, but for high-speed motion, the signal-to-noise ratio will be reduced, which will cause the satellite to lose lock and take a few minutes to relock, which affects many applications. After adding the C / A code to L2, civilian users can directly adopt the method similar to the PPS positioning of privileged users to eliminate the effect of the ionosphere, reducing the typical ionospheric error of 7.0m to 0.1m, SPS standard positioning The accuracy will be increased to 8.5m (95% confidence). For the life-critical civil aviation, due to the existence of many navigation equipment and radar using frequency bands close to L, it will cause interference to GPS. If you cancel all use close to this The frequency band system requires a lot of cost. The better way is to add a new GPS carrier signal with a wider frequency band for civil navigation purposes. Finally, IGEB chose another design that is designed to improve the current civilian state. Its energy ratio The existing L is increased by 6dB, which enhances the ability to resist other interference signals. While improving the satellite and the signal, the ground control part (OCS) of the system will also be upgraded, mainly including: new type digital receiver and computer upgrade dedicated GPS monitoring station, replace the antenna of the monitoring station; replace the computer workstation of the current GPS ground main control station with a distributed structure; Control network integration, complete R capability; complete the full operation capacity of the standby main control station of Wandunbao Air Force Base; increase F command and control functions. The ground monitoring network plays the role of monitoring satellite health status, daily maintenance, determining satellite ephemeris and clock Parameters, upload satellite data and other functions. In the current configuration, each master station uses its own small Kalman filter called a partition to estimate the orbit and clock difference of the GPS satellite and the clock difference of the receiver of the monitoring station. The difference correction parameters are uploaded to each satellite. After using dual-frequency observations to eliminate atmospheric delay errors, ephemeris and clock errors become the main items. For the current GPS constellation, the effects of ephemeris and clock errors are 8m, respectively, and the corresponding user equivalent ranging error (UERE) is After adopting precision improvement plan A at 2.3m, the user UERE of GPS ephemeris and clock error will be reduced to 1.25m. This is achieved by adding monitoring stations operated by 6-14 National Image and Survey Bureaus to the system The main control station uses single-zone Kalman filtering to achieve the improvement of GPS standard positioning accuracy
Qunsuo is a professional manufacturer of Barcode Scanner, we have plenty years of experience in this industry. We provide 1D Barcode Scanner and Qr Code Scanner , help customers from various industries. All of our barcode scanner support connecting with Android IOS via bluetooth. Furthermore, Our barcode scanner also support connecting with PC via 2.4G wireless module. And our QS-S03 is equipped with Zebra scanner engine. If any interests of our Wireless Handheld Barcode Scanner, please feel free to send inquiry to us for more information.
Wireless Handheld Barcode Scanner,Handheld Inventory Scanner,Hand Barcode Scanner,Handheld Qr Code Scanner
Shenzhen Qunsuo Technology Co., Ltd , https://www.qsprinter.com