The Global Positioning System (GPS) is a global, omnipotent (land, ocean, aerospace, and space), all-weather navigation positioning, timing, and speed measurement developed by the US military in the early 1970s. The system consists of three subsystems: a space satellite system, a ground monitoring system, and a user receiving system. It has been widely used in many fields such as military and civilian use. In developed countries, GPS technology has begun to be used in transportation and road engineering. At present, China's application in this area has just started. Application of GPS in Road Engineering Materail Bin Storage,Wheelie Bin Storage,Metal Bin,Stackable Metal Bin,Stacking Bin Suzhou Malltek Supply China Co.,Ltd. , https://www.oktrolley.com
In road projects, GPS is currently used to establish various road engineering control networks and to measure air traffic control points. The rapid development of high-grade highways imposes higher requirements on surveying technology. Because the lines are long and there are few known points, it is difficult to meet the high-precision requirements by using conventional measurement methods. At present, China has gradually adopted GPS technology to establish the first-level high-precision control network, such as the Shanghai section of Shanghai-Nanjing Expressway and the Shanghai-Hangzhou Expressway. The first-level control network was established using GPS, and conductors were then encrypted using conventional methods. Practice has proved that the point error within a few tens of kilometers is only about 2cm, which has reached the precision that is difficult to achieve with conventional methods, and at the same time greatly advances the construction period. The Zhejiang Provincial Bureau of Surveying and Mapping used the fast static positioning function of the Wild 200 GPS receiver to measure all the initial test leads of the line, and quickly and accurately established the hundreds of kilometers of expressway control network, achieving good results.
GPS technology is also applied to the control measurement of large bridges. Because there is no need for viewing, it can form a strong mesh shape, improve the accuracy of the point, and it is also very effective for detecting the fulcrum of the conventional measurement. For example, in the construction of the Jiangyin Yangtze River Bridge, a high-precision corner network was first established using conventional methods, and then GPS was used to detect the network. The GPS detection network reached millimeter-level accuracy, which is in good agreement with the conventional precision network. GPS technology also has a wide range of application prospects in tunnel surveying, and its measurement does not require visual communication, which reduces the intermediate steps of conventional methods. Therefore, it is fast, accurate, and has obvious economic and social benefits.
Differential dynamic GPS is mainly used in road surveying data acquisition of digital ground model, encryption of control points, midline stakeout, longitudinal section survey, and airborne GPS aerial survey without external control points. In June 1994, the KART real-time phase-difference satellite positioning system was tested at Tongji University, achieving an accuracy of better than 2cm in a range of 1km. Therefore, it can be used for encryption of line control networks. The GPS measurement contains three-dimensional information that can be used for digital ground model data acquisition, midline stakeout, and profile measurement. At the same time as the lofting at the midline plane position, a vertical section can be obtained. In the midline lofting, the data of the reference station needs to be transmitted from the data link to the mobile station in real time, thereby providing the real-time position of the mobile station. Because the GPS instrument does not indicate the direction as the theodolite, it needs to be combined with the CAD system so that the difference between the current position and the design coordinates can be seen on the computer screen. The airborne dynamic differential GPS is applied to aerial surveys. It has been successfully implemented in Germany and Canada. The three-dimensional coordinates of each photographic center are measured by using carrier phase difference, and no external control point measurement is needed, and good results are obtained.
Application of GPS in Car Navigation and Traffic Management
Three-dimensional navigation is the primary function of GPS. Aircraft, ships, ground vehicles, and pedestrians can all use GPS navigation receivers to navigate. Car navigation system is a new technology developed on the basis of GPS. It consists of GPS navigation, autonomous navigation, microprocessors, speed sensors, gyro sensors, CD-ROM drives, and LCD displays.
GPS navigation is the GPS receiver receives GPS satellite signals (more than three), get the point latitude and longitude coordinates, speed, time and other information. In order to improve the accuracy of car navigation and positioning, differential GPS technology is usually used. When the car travels to the cover of underground tunnels, high-rise buildings, highways, etc. and does not capture GPS satellite signals, the system can automatically import the autonomous navigation system. At this time, the car speed sensor detects the car's traveling speed through the micro-processing unit. In data processing, the forward distance is directly calculated from the speed and time. The gyro sensor directly detects the direction of advancement. The gyroscope can also automatically store various data. Even if the tire is temporarily parked, the system can be reset.
The position coordinates and direction of the car measured by GPS satellite navigation and self-discipline navigation have certain errors from the actual route trajectory. In order to correct the error between the two and make it consistent with the route on the map, a map must be used. Matching technology, plus a map matching circuit, real-time correlation of the car travel route and the error on the road in the electronic map, and do automatic correction, at this time, the map matching circuit through the micro-processing unit for fast processing, get the car The correct position on the electronic map to indicate the correct driving route. The CD-ROM is used to store information such as road data, and the LCD display is used to display navigation related information.
The combination of a GPS navigation system, an electronic map, a radio communication network, and a computer vehicle management information system can realize many functions such as vehicle tracking and traffic management. For example:
Vehicle tracking
GPS and electronic maps can be used to display the actual position of the vehicle in real time, and can be zoomed in, zoomed out, restored, and replaced; the target can be moved to keep the target on the screen at all times; multiple windows, multiple vehicles, and multiple screens can also be implemented simultaneously. Tracking, use this function to track and transport important vehicles and goods.
2. Provide travel route planning and navigation
Planning travel routes is an important auxiliary function for car navigation systems, including:
• Automatic route planning The driver determines the start and end points, and the computer software automatically designs the best driving route according to the requirements, including the fastest route, the simplest route, and the route with the least number of highway segments.
・Manual circuit design The driver automatically creates a line library by designing the starting point, end point, and passing point according to his or her destination. After the circuit planning is completed, the display can display the design circuit on the electronic map, and at the same time, display the vehicle running path and operation method.
3. Information query
Provide users with the main objects, such as tourist attractions, hotels, hospitals and other databases, users can make inquiries on the electronic map as needed. Query data can be displayed in text, language, and images, and its location can be displayed on an electronic map. At the same time, the monitoring center can use the monitoring console to inquire about the location of any target in the area, and the vehicle information will be digitally displayed on the electronic map of the control center.
4. Traffic command
The command center can monitor the operation status of vehicles in the area and make reasonable dispatch of the monitored vehicles. The command center can also talk with the tracked target at any time and implement management.
5. Emergency assistance
The GPS positioning and monitoring management system can provide emergency assistance to vehicles that are in danger or have accidents. The electronic map of the monitoring station can display help information and alarm targets, plan out the best assistance scheme, and use the alarm sound and light to remind the on-duty personnel to handle the emergency.
The research and application of GPS technology in car navigation and traffic management engineering has just started in China, and foreign research in this area has already begun and has achieved certain results. The University of Calgary, Canada, designed a dynamic positioning system that includes a strap-down inertial system, two GPS receivers, and a microcomputer that can measure linear parameters of existing roads and serve road management systems. The United States has developed a road traffic management system applied to cities. The system uses GPS and GIS to establish a road database. The database contains various current data, such as the exact location of roads, road conditions, and roadside facilities. The system was established in 1995. The official operation of the year has played an important role in urban road traffic management.
In recent years, various systems for vehicle induction have been developed abroad, and the determination of the vehicle position in real time mainly relies on inertial measurement systems and wheel sensors. With the development of technology, GPS has a great tendency to replace the first two methods. The GPS location used for city vehicle guidance is generally to set up a reference station in the city. The on-board GPS receives the information transmitted by the reference station in real time. After differential processing, the real-time location can be calculated, and the current location and the target to be reached are on the road. The optimization calculations in the network can show the optimal route to the target on the road electronic map, and serve the public security, fire protection, emergency repair and emergency vehicles.
GPS is one of the most innovative new technologies developed in recent years and will inevitably be used more and more widely in many fields. It is believed that with the development of China's economy, as well as the rapid construction of high-grade highways and the gradual deepening of the application of GPS technology, its application in road projects and transportation will be more extensive and in-depth, and will play a greater role.