Discussion on the application prospect of the hott

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Discussion on the application prospect of GPS technology in Highway Survey

the application of GPS technology in highway survey is a major technological revolution in highway field survey, and its application and development prospects are very broad. In particular, real-time dynamic (RTK) positioning technology contains great technical potential in highway survey. This paper mainly introduces the application of GPS and the expanding loss range of paper enterprises in Highway Survey and its great role in promoting highway survey

key words: GPS; RTK; Static positioning; Dynamic positioning

1 current situation of GPS technology development

globalpositioningsystem (GPS) is a satellite navigation system jointly developed by the U.S. Army, navy and air force. It has global, all weather, continuous, real-time navigation, positioning and timing functions, and can provide precise three-dimensional coordinates, speed and time for all kinds of users. Single point navigation and relative geodesic positioning are two aspects of GPS application; Relative geodesic positioning is the main application method for conventional measurement

relative geodesic positioning uses L1 and L2 carrier phase observations to achieve high-precision measurement. Its principle is to use the local difference method of carrier phase measurement: calculate the primary difference between receivers, calculate the secondary difference between receivers and satellite observation epochs, and calculate the length of the undetermined baseline through two difference calculations; Solving the integer ambiguity is the key technology. According to the algorithm model, static, fast static and RTK operation modes are designed. The static operation mode is mainly used for high-precision measurements such as crustal deformation observation, national geodesy and dam deformation observation; Fast static measurement is widely used in general engineering measurement because of its high efficiency and centimeter accuracy; RTK measurement is widely used in data acquisition (such as detail measurement) and engineering setting out because of its fast real-time, centimeter accuracy and other characteristics. RTK technology represents the mainstream of GPS relative geodesic positioning application

gps geodesic receiving equipment is the basic condition for realizing geodesic positioning. The receiver can be divided into single frequency and dual frequency. The dual frequency can correct the ionospheric refraction effect with L2 observation value, which is most suitable for medium and long baseline (greater than 20km) measurement. It has the function of fast static measurement and can be upgraded to RTK function; The single frequency machine is suitable for short baseline measurement less than 20km, and has a good performance price ratio for general engineering measurement. RTK system is composed of GPS receiving equipment, radio communication equipment, electronic hand book and supporting equipment. The whole set of equipment has the characteristics of lightweight, easy operation, real-time reliability, centimeter accuracy and so on, which can fully meet the requirements of data acquisition and engineering setting out. In view of the limited number of on orbit satellites of the GPS system, the normal solution cannot be guaranteed under the condition that the intervisibility is blocked, which affects the accuracy and reliability of positioning. Practice shows that single frequency GPS system has great limitations due to the constraints of multiple environments. With the continuous improvement of Russia's global navigation satellite system (clonass), the dual constellation system (glonass+gps) using GLONASS to improve GPS performance has been successfully developed by ASHTECH company of the United States. This all-weather, all terrain, high-precision system provides users with more perfect receiving equipment, and the receiving equipment of the dual constellation system is a new level of GPS receiving equipment

2 application prospect of GPS technology in highway surveying

with the implementation of the western development with the rapid growth of China's national economy, the construction of high-grade highways in our province has ushered in unprecedented development opportunities, which puts forward higher requirements for survey and design. With the development of software technology and hardware equipment in the highway design industry, highway design has realized CAD, Some software itself also requires the support of ground digital surveying and mapping products; Establishing a data link integrating survey, design, construction and later management, and reducing intermediate links such as data transcription and input are the requirements of "integration of internal and external industries" in Highway Survey and design, and also the "bottleneck" affecting the development of high-grade highway design technology. At present, although electronic total station and other advanced instruments and equipment have been used in highway survey, the conventional measurement methods are limited by horizontal intervisibility and operating conditions, with high operation intensity and low efficiency, which greatly extends the design cycle. The progress of survey technology lies in the introduction of equipment and technological transformation. Under the current technical conditions, the introduction of GPS technology should be the first choice. At present, GPS static or fast static methods are used to establish the overall control survey along the line, so as to provide the basis for mapping the strip topographic map and route plane and longitudinal survey in the survey stage; Establishing construction control for bridges and tunnels in the construction stage is only the primary stage of the application of GPS in highway surveying. In fact, the technical potential of highway surveying lies in the application of RTK (real-time dynamic positioning) technology. The application of RTK Technology in highway engineering has a very broad prospect. The following is a brief introduction to the application of RTK Technology in highway survey

3 application of RTK Technology in highway surveying

3.1 introduction to real-time dynamic (RTK) positioning technology

real time dynamic (RTK) positioning technology is a real-time differential GPS (rtdgps) technology based on carrier phase observations. It is a new breakthrough in the development of GPS measurement technology and has broad application prospects in highway engineering. As we all know, in both static positioning and quasi dynamic positioning modes, due to the lag of data processing, the positioning results cannot be calculated in real time, and the observation data cannot be checked, which makes it difficult to ensure the quality of the observation data. In practical work, it is often necessary to rework to re measure the unqualified observation results caused by gross errors. The main method to solve this problem is to change from target oriented management to opportunity oriented management, and extend the observation time to ensure the reliability of measurement data, which reduces the efficiency of GPS measurement

the real-time dynamic positioning (RTK) system is composed of a reference station and a mobile station. The establishment of wireless data communication is the guarantee of real-time dynamic measurement. Its principle is to take the primary control point with high point accuracy as the reference point, place a receiver as the reference station, and continuously observe the satellite. While receiving the satellite signal, the receiver on the mobile station receives the observation data on the reference station through the radio transmission equipment, The random computer calculates and displays the three-dimensional coordinates and measurement accuracy of the flow station in real time according to the principle of relative positioning. In this way, the user can monitor the data observation quality of the points to be measured and the convergence of the baseline solution results in real time. According to the accuracy of the points to be measured, we can determine the observation time according to whether the experimental machine is sold abroad, and whether our Jinan trial is in Jinan, which is a few manufacturers' standard, so as to reduce redundant observations and improve work efficiency

3.2 application

real time dynamic (RTK) positioning has two measurement modes: fast static positioning and dynamic positioning. The combination of the two positioning modes can cover highway survey, construction setting out, supervision and GIS (Geographic Information System) front-end data collection in highway engineering

3.2.1 fast static positioning mode

GPS receiver is required to conduct static observation on each mobile station. During the observation process, the synchronous observation data of the reference station and the satellite are received at the same time, and the whole week unknowns and the three-dimensional coordinates of the user station are solved in real time. If the change of the solution results tends to be stable and its accuracy has met the design requirements, the real-time observation can be ended. It is generally used in control measurement, such as control encryption; If conventional measurement methods (such as total station measurement) are used, it is greatly affected by objective factors, and it is difficult to implement in areas with poor natural conditions. However, rapid static measurement with RTK can achieve twice the result with half the effort. Single point positioning only needs min (with the continuous development of technology, the positioning time will be shortened), which is less than one fifth of the time required for static measurement. In highway measurement, it can replace the total station to complete traverse measurement and other control point encryption work

3.2.2 dynamic positioning

static observation at a control point for several minutes (some instruments only need 2 ~ 10s) for initialization before measurement, and then the mobile station can automatically observe according to the predetermined sampling interval, and together with the synchronous observation data of the reference station, determine the spatial position of the sampling point in real time. At present, its positioning accuracy can reach centimeter level

the dynamic positioning mode has a broad application prospect in the highway survey stage, which can complete topographic map mapping, center pile surveying, cross-section surveying, vertical section ground line surveying, etc. Measuring 2 ~ 4S, the accuracy can reach 1 ~ 3cm, and the whole measurement process does not need intervisibility, which has incomparable advantages of conventional measuring instruments (such as total station)

3.3 advantages of RTK Technology

3.3.1 real time dynamic display of centimeter accuracy measurement results (including elevation) that have been tested by reliability

3.3.2 completely get rid of the rework caused by gross error, and improve the efficiency of GPS operation

3.3.3 the operation efficiency is high. Each setting out point only needs to stay for 1 ~ 2S, and the mobile station group works. Each group (3 ~ 4 people) can complete the centerline measurement of 5 ~ 10km. If it is used for topographic survey, each team can complete 0.8 ~ 1.5km3 topographic map mapping every day, and its accuracy and efficiency are unmatched by conventional survey

3.3.4 complete the leveling of middle piles while setting out the center line

3.3.5 wide application range - it can cover many aspects such as highway survey (including horizontal, vertical and horizontal), construction setting out, supervision, completion survey, maintenance survey, GIS front-end data acquisition

3.3.6 if the corresponding software is assisted, RTK can work together with the total station to give full play to their respective advantages

3.4 promotion suggestions

3.4.1 the combination of GPS static positioning technology and dynamic positioning technology can complete highway horizontal control survey efficiently and accurately

3.4.2 the combination of conventional methods and GPS technology in the production process can greatly improve the production efficiency

3.4.3 with the development of RTK technology, which is the characteristic of GPS technology, various manufacturers have successively introduced instruments with independent patented technology. Its initialization time is shorter and shorter, its tracking ability is stronger and stronger, its accuracy is higher and higher, its reliability is stronger and stronger, and it has a good cost performance. In the survey and design units, there is a trend to replace the total station, and this factor should be considered when updating the unit equipment

3.4.4 the application of GPS technology in highway survey is a revolutionary technological innovation of highway survey, which will update the traditional operation concept

4 Conclusion

the application of GPS in highway survey has revolutionized the survey means and operation methods of high-grade highways, and greatly improved the survey accuracy and efficiency. In particular, real-time dynamic (RTK) positioning technology will have broad application prospects in highway survey, construction and later maintenance and management. (end)

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