1.1 System composition
The main purpose of this document is to introduce the design scheme of Beidou high-precision positioning based on the current basic situation of vehicle terminals.
1.2 Requirement Overview
With the emergence of high-precision positioning demands from two passengers and one danger, ports, airports, mines, thermal power plants, agricultural machinery, forklifts, military vehicles, special vehicles, and other industries, users of vehicles in many industries are no longer satisfied with the 10-20 meter positioning accuracy of GPS and hope to improve it to centimeter level, decimeter level, sub meter level, and meter level accuracy. Two passengers and one danger need to be located at sub meter level, so as to determine which lane to drive on. The monitoring and management department can monitor whether the vehicle is illegally driving on the fast lane, whether the turning speed exceeds the standard, etc., to better ensure vehicle safety.
1.3 Scheme Introduction
In response to these demands, Zhengzhou Beidou Seven Star Communication Technology Co., Ltd. has launched a series of high-precision satellite receiver products, which comprehensively apply various global satellite positioning systems such as Beidou, GPS, GLONASS, Galileo, etc., achieving centimeter level, decimeter level, sub meter level, meter level positioning accuracy, as well as directional accuracy of 0.05 °, 0.1 °, and 1 °. The products include high, medium, and low-end system products, with prices ranging from a few hundred yuan, a few thousand yuan, to tens of thousands of yuan, meeting the requirements of different industries for different precision, performance, and price.
Our positioning technology is divided into two types: ground differential and satellite based differential
Ground differential
Ground differential accuracy is higher, but ground differential signals are required. Differential signals can be provided by our differential reference station products or obtained through ground-based wide area enhancement networks for a fee. A wireless communication module is required to receive differential data. 
Star based differential
The accuracy can reach sub meter and meter level, automatically receiving differential signals from satellites without any cost. No need for differential benchmark station procurement costs or ground wide area enhanced network service fees. No need for a wireless communication module to receive differential data. We will also combine inertial navigation, wheel speed, laser, wireless, labeling, vision, map matching and other methods to customize and develop a complete navigation solution for seamless positioning and navigation, unmanned vehicles, unmanned agricultural machinery, unmanned forklifts, unmanned sweepers, AGVs and other applications.

1.4 Beidou Seven Star Products
1) Centimeter level high-precision satellite receiver (reference station)
Equipped with high-precision positioning function and reference station function
Support satellite systems such as Beidou, GPS, GLONASS, Galileo (optional), SBAS, QZSS, etc
Position accuracy is 1cm+1ppm RMS
2) Centimeter level high-precision positioning and directional satellite receiver
Adopting dual antennas, it has high-precision positioning and direction measurement functions, including vehicle static and dynamic direction measurement
Support satellite systems such as Beidou, GPS, GLONASS, Galileo (optional), SBAS, QZSS, etc
Position accuracy is 1cm+1ppm RMS
3) Low cost centimeter/sub meter satellite receiver
This type of receiver has better accuracy in open space applications, but its accuracy may decrease in slightly worse environments
Support satellite systems such as Beidou, GPS, GLONASS, Galileo (optional), SBAS, QZSS, etc
Position accuracy is centimeter level/decimeter level/sub meter level
4) Satellite based differential high-precision satellite receiver
Lower cost
The receiver can obtain differential signals from satellites and achieve sub meter level positioning
Support satellite systems such as Beidou, GPS, GLONASS, Galileo (optional), SBAS, QZSS, etc
The position accuracy is sub meter level
The system application is simple and convenient
1.4.1 Flow Chart for Data Transmission Design
(1) The Beidou base station transmits differential data to the server, and the vehicle mounted terminal device transmits location data to the server through a 4G module. Based on the principle of nearest latitude and longitude, the device receives the nearest base station's differential data and calculates high-precision coordinates.
The following figure represents the transmission method and flowchart of base station query data.

(2) Monitoring System Flowchart

2. Core technology and structural design of the system
2.1 Core Technologies of System Architecture
Beidou high-precision positioning technology is a key core technology for sub meter level high-precision positioning terminals, which can achieve sub meter level high-precision positioning by adopting this technology. This technology is based on the BeiDou satellite navigation system currently being implemented in China. In the area covered by Beidou satellite signals, differential working mode is adopted between Beidou base stations and locomotive equipment. Base stations have the characteristics of low construction cost, wide coverage, strong practicality, and long-term reliable operation. Locomotive equipment has the characteristics of small size, light weight, reliable operation, and stable positioning results (low drift). The communication link can adapt to various working environments and has the characteristics of long-term stable operation.
Beidou high-precision positioning technology utilizes Beidou local differential technology to improve positioning accuracy. This technology is based on Beidou's carrier phase differential RTK to achieve sub meter level high-precision positioning. Local differential working principle: Place a Beidou receiver at a precise point with a known position as a differential base station. The base station broadcasts the corrected position information and RTK information through a communication link. The locomotive equipment receives the differential information broadcast by the base station and, together with its own measured data, can solve for its high-precision position information. The high-precision position information is then uploaded to the monitoring center to achieve high-precision positioning.