/ Chaowen News/August 03, 2022 GUANGZHOU -- "Scientific and technological self-reliance is the foundation for national prosperity and security." On July 31, 2020, the Beidou-3 navigation satellite system completed its global network, which means that the major infrastructure of space-time information has been fully under its own control. In the past two years, the application of the Beidou System has built a mature industrial chain. Similarly, only through independent innovation can we control the lifeblood of science and technology in our own hands.
A few days ago, Chihiro Position "six pulse Shenjian" six bottom technology series surfaced, today we look at how Chihiro Position break through the non-area station rapid convergence PPP technology, to provide fast, efficient, reliable and high-precision positioning services anywhere in the world.
"In previous years, the signal of the equipment is often unstable, sometimes there is no signal." Xinjiang Tacheng corn farmer Bao master said.
Tacheng is located in the northwestern border region of Xinjiang, where the communication network is often interrupted. The automatic navigation equipment can overcome the problems of lack of network signal and insufficient coverage of regional station network, and quickly realize centimeter-level high-precision operation.
Behind this, rely on the Qianxun position algorithm engineers on the convergence performance of space-based enhanced positioning technology - in the absence of relying on satellite navigation area encryption station, without the aid of atmospheric products, still can quickly and reliably obtain high-precision positioning results, convergence time of 1 minute on average, the fastest can reach convergence in tens of seconds.
"We call this technology as area-free station rapid convergence PPP technology, which is independent of atmospheric products, can greatly reduce the cost of global station construction, and can achieve satellite/network dual-link global coverage through small broadcast bandwidth." Chihiro position advanced algorithm expert Xu Kun said.
Qianxun Location is the first company in China to acquire this technology capability and put it into commercial operation. It can provide fast, efficient and reliable high-precision positioning services anywhere in the world.
Convergence time: The "secret" of traditional PPP technology
The main reason why agricultural machinery autonomous driving equipment relies on network and regional station network is that most of them use real-time dynamic positioning RTK technology. Although the traditional RTK technology converges quickly, its coverage is still limited. The location target must be in the range of communication signal coverage, in the sea, desert, overseas and other areas, the formation of a large range of location blind area.
Complementing it is the precision single point positioning PPP technology. PPP technology can accurately model satellite positioning errors and broadcast them to users, so as to get rid of the dependence of data transmission on the Internet. Users can also obtain accurate positioning results through satellite links.
However, the traditional PPP technology usually takes ten to dozens of minutes to converge to the centimeter-level accuracy of the initial positioning time. Such a long time obviously cannot meet the requirements of UAV flight control, agricultural aircraft navigation, intelligent driving and other high-real-time and high-precision application scenarios. How to shorten the PPP initialization time is an important factor to improve user experience.
Shorten the convergence time, a contest about time
With the improvement of the global networking of Beidou navigation satellite system and Galileo Navigation satellite system, as well as the upgrade of the multi-system support of the terminal receiver, the convergence time of multi-system PPP technology has been significantly improved with the support of the fixed PPP ambiguity technology. From tens of minutes to ten minutes.
When the industry is generally satisfied with the PPP convergence time of better than 10 minutes, the Chihiro Location technical team did not stop there, but considered how to effectively apply the multi-system and multi-frequency satellite navigation signals. On the basis of the global framework station of Qianxun Location, the server algorithm and terminal algorithm continue to make breakthroughs to improve the convergence performance of PPP and the convergence time index.
With the construction of the Beidou-3 global System, Qixun Position rapidly deployed and built hundreds of framework stations around the world that can support tracking of the full-frequency satellite signals of the whole Beidou-3 system, and synchronously provide global enhancement services. "With the support of Beidou's global service and our natural advantage of having a global framework station, it provides a strong guarantee for calculating high-precision satellite-side error correction products, which allows us to see the possibility of improved PPP convergence performance." Chihiro location algorithm expert Chang Shengqi said.
With the support of the global frame station, in the server-side algorithm level, the high-precision satellite orbit clock difference products are the basis for realizing the rapid convergence of PPP. Especially for the new navigation system Beidou-3, it is a great challenge to accurately model the satellite's attitude change law and solar pressure. By tracking the dynamics of the academic frontier and combining with the long-term tracking data of the Global Framework Station of the Qianxun position, the algorithm experts of the Qianxun position have conducted in-depth research on the motion law of the Beidou-3 satellite, and established the high-precision satellite attitude model and optical pressure model, which has laid the foundation for the high-precision satellite orbit clock error product calculation.
The satellite hardware delay product of multi-frequency and multi-system is also an important module for realizing PPP fast convergence at the server algorithm level. Thanks to Qianlong time server with unified hardware configuration, the satellite hardware delay product of Qianxun position solution is more stable and accurate. In addition, in order to maximize the effect of rapid convergence, the cloud integrated PPP engine plays a key role.
The key for users to obtain the best PPP fast convergence experience is to broadcast the above server products to users in the shortest time. "The Global Frame station at the Chihiro location sends data back through dedicated lines, which greatly ensures the 'freshness' of the observations. The fast processing capability of massive data, distributed and parallel algorithmic scheduling architecture, and flexible and efficient broadcast link design enable service products to be delivered to customers via geostationary satellites in seconds." Chihiro position senior technical expert Chen Jianbo said.
With complete and reliable server algorithm products, flexible and efficient broadcast link design, how to achieve PPP ultra-fast convergence on the terminal side? The terminal algorithm team explores new technical paths from the application of multi-frequency observations and fixed PPP ambiguity to improve convergence performance.First, at the application level of multi-frequency observation values, a set of self-adaptive multi-frequency observation model is deposited by combining the multi-dimensional spatio-temporal data of different geographical environments accumulated by the "One Net" of the National Beidou Foundation Enhancement System. The model can be adaptive adjusted according to the characteristics of the actual frequency type and observation noise.
Secondly, at the level of fixed PPP ambiguity, combining the accuracy and delay of star-base correction, random characteristics of observation value, residual error of observation value, etc., various methods including empirical model tuning and machine learning were tried to confirm the ambiguity, and a PPP fixed ambiguity model adapted to broadcast star-base correction of satellite link was formed. To ensure that the terminal can obtain reliable positioning results when the satellite link signal is interrupted by short time. < / p > < p > < b > operational monitoring, maintain stable convergence < / b > < / p > < p > 6 minutes, 3 minutes, 2 minutes, 1 minute... Every increase in speed is the motivation to continue to break through. Through a series of technical iterations and attempts, the average convergence time of the chihiro position is stable at about 1 minute, and the fastest convergence time is only tens of seconds. The bigger problem is how to maintain the stability of convergence performance.
On the service side, through more than 6 years of service experience, Qianxun Position has accumulated rich service anomaly monitoring means. From the base station data, satellite status, product accuracy, link delay and other dimensions, it has built a complete operation and maintenance monitoring system to ensure the stability of service product calculation and data broadcasting.
At the terminal side of the product, a complete set of R&D, testing, pre-sale and after-sales monitoring system has been established based on the self-developed star base module, board card, complete machine and other equipment. Through the accumulation of a large number of application scenarios and cases, the terminal algorithm level has been iteratively upgraded.
High precision location service can be obtained in seconds anywhere in the world. The breakthrough of PPP convergence speed enables more efficient operation of high-real-time and high-precision application scenarios such as automated agriculture, Marine survey and UAV inspection, and also provides a broader space for the global application of satellite navigation technology in intelligent driving and other fields.
