Research On BeiDou/GPS Dual-Mode Positioning Vehicle Terminal

Beidou satellite navigation system is a global satellite navigation system independently developed and operated by China, and it is also an important infrastructure being established for spatial information. Beidou satellite navigation system will break up monopolies of foreign technologies and ease their restrictions in Chinese technologies. Moreover, Beidou satellite navigation system enables China to have autonomy in the military field, and plays an important role in national security protection and economic development. By combining the two navigation systems, and making every possible use of its redundancy measurements, we can obtain an integrated navigation system with high accuracy and good fault tolerance. As Beidou system is still under construction, its positioning accuracy is not high enough in most areas except for some specific areas. Therefore, integrating GPS and Beidou in a terminal can guarantee its positioning accuracy and reliability. The combination of GPS and Beidou systems will enhance validity and reliability of Chinese positioning system, helping Beidou navigation system go global.This research project combines the Beidou and GPS navigation systems, and investigates the positioning functions of a terminal with both navigation systems. The terminal is applied in vehicles with the capabilities of capturing the status of the vehicle, positioning and tracking, signal detection, remote packet transmission, scheduling and management of vehicles. The integrated terminal consists of five parts, power supply module, microcontroller unit (MCU), data collection and control, remote data transmission, and positioning modules. Based on comparison of various schemes, each module is provided with a specific implementation solution. The current scheme selects STM32 series chips that are based on the Cortex-M3 core as the central processor, and UC/OS â…¡ as the operating system. The MCU receives positioning data from ATGM331C, and information of ACC, door switches and others, and sends them to other applications, after analysis and repackaging, via remote data transmission module such as a mobile phone, or the Internet.The terminal adopts multi-threaded mode as the communications network architecture. Message communication mechanism, UART interface to send and receive messages and GPIO port change all use interrupt mode. This paper presents some of primary threads, including the thread of data acquisition, the thread of signal control, the thread of positioning packet processing, the thread of remote data transmission module. The NMEA0183 protocol and related specifications are described in this paper. Serial ports were used to receive positioning data and MCU extracted the required information after receiving data. This paper gives the program design for positioning data analysis. Through the terminal, users can use the GIS vehicle monitoring platform to locate and track vehicles, monitor traffic, schedule remotely, thereby ensuring the normal operation of vehicles.