The words satellite-based augmentation system appear more and more frequently in RTK. Someone asked me if the satellite-based augmentation system is helpful for our measurement. What kind of system is this? Today, the editor will give you a detailed explanation of the satellite-based augmentation system. By the way, I will also explain the ground-based augmentation system and the difference between the two.
Both the satellite -based augmentation system and the ground-based augmentation system are "supplements" to the global mainstream satellite navigation systems. The chairman of Sinan Wang Yongquan said that their main difference lies in the source of the received signal. One is in the "sky" and the other is in " underground". Why do you say that, because they use geosynchronous orbit satellites and ground communication methods.
In fact, the difference between the two can best be distinguished from the perspective of the service target.
Foundation reinforcement system
Since the ground-based augmentation system is a supplement to the satellite navigation system, let’s talk about the satellite navigation system first. I believe everyone knows how the satellite navigation system locates. When the receiving device receives the signals of 4 or more navigation satellites, it can be calculated. Out of its location. But the accuracy of this positioning method is about 10m.
However, the simple satellite navigation positioning accuracy (10m) is far from enough for most industrial applications and military fields.
In order to improve the positioning accuracy, by people on the ground construction established fixed reference station (CORS station) acquires the measurement error in the satellite positioning. Then, the result of the "correction number" after comparing the satellite positioning coordinates with its own precise coordinates is sent to the receiver. This resulted in the later foundation enhancement system.
For example, local surveying and mapping, land, and meteorological departments are responsible for building the CORS network of national continuous operation reference stations, which is a ground-based enhancement system. Later, the China National Beidou Foundation Enhancement System , which was built by China North Industries Group, Ministry of Land and Resources, Ministry of Transportation, National Bureau of Surveying and Mapping, National Earthquake Administration, China Meteorological Administration, Chinese Academy of Sciences, and Qianxun Position Network Co., Ltd., also belong to the foundation enhancement system. .
The ground-based augmentation system is a multi-faceted and in-depth product of high-tech technologies such as satellite positioning technology, computer network technology, and digital communication technology. By providing differential correction signals, the accuracy of satellite navigation can be improved;
The ground-based augmentation system mainly serves ground applications , covering professional fields such as surveying and mapping, monitoring and control, driving test and driving training, precision agriculture, aviation and navigation, as well as public fields such as traffic navigation, tourism, and emergency rescue. By receiving the differential correction signal provided by the ground reference station network, to achieve the purpose of improving the accuracy of satellite navigation, the optimized positioning accuracy can range from millimeter to submeter level.
Although the accuracy of foundation enhancement is high, the coverage area is limited. The positioning target must be within the coverage of the communication signal, but in the high altitude, sea, desert and mountainous area where the communication signal is difficult to cover, a large-scale positioning blind area is formed.
In order to solve the needs of a larger range of high-precision positioning, people upload the correction parameters obtained from the reference station to the satellite, and then broadcast it to the world through the satellite. In this way, the user terminal does not have to be restricted by communication capabilities. Star-based enhancement also comes from this.
Satellite-based augmentation system
The satellite-based augmentation system, English name SBAS (Satellite-Based Augmentation System), is equipped with a satellite navigation augmentation signal transponder through a geostationary orbit (GEO) satellite, which can broadcast ephemeris error, satellite clock error, ionospheric delay, etc. Revise the information to improve the positioning accuracy of the original satellite navigation system.
The reason for the emergence of satellite-based augmentation systems is also described above. The main reason is to make up for the deficiencies of ground-based augmentation systems and to solve the problem of communication capacity limitations due to geographical restrictions.
To be more careful, it is because the continuous operation reference station (CORS) cannot be established as a reference station in the air and at sea, and the local differential technology on the ground cannot be used.
Therefore , the various parts of the positioning error (ephemeris error, atmospheric delay, etc.) can only be calculated through the model through the wide-area differential technology , and then the correction information is sent to the user in the form of a satellite signal , and the user finally combines the correction information according to the correction information. The specific position is used to calculate each error and correct the observation value.
SBAS working principle
If the ground-based augmentation system mainly serves ground applications, then the satellite-based augmentation system has more advantages in aviation and navigation applications . This is also the most direct manifestation of the difference between the two.
Regarding satellite-based augmentation systems, domestic RTK manufacturers are actually doing it. "China Precision" (Atlas) , the users of UniStrong must have heard of it. As the first satellite-based enhanced service system in China, it was first proposed by UniStrong in November 2013 and officially provided commercial services to global users in 2015. Later, China Haida also launched the " Global Precision (Hi-RTP) " satellite-based enhancement service. And Qianxun's more "radical" satellite-ground integration "Sky Sound Project" , which combines satellite-based enhancement + ground-based enhancement, to provide users with high-precision, high-reliability, real-time and seamless high-precision space-time services.
The ground-based enhancement system has changed the traditional RTK measurement operation mode. The user does not need to set up a reference station during the measurement, and can be operated as a stand-alone machine, and the working range is expanded, and the work efficiency can be improved.
The emergence of satellite-based augmentation systems has made up for the deficiencies of ground-based augmentation systems. In places where it is difficult to establish ground base stations or insufficient communication signals, such as deserts and sea areas, satellite-based augmentation systems can provide us with high-precision positioning services.
