Data Processing And Precision Analysis In RTK Positioning For Offshore Piling

Since GPS (Global Positioning System) technology come out in 1970s, it has been used widely in the fields of navigation, surveying and communication etc, and got a more and more significant role in national economic and modernization construction. RTK (Real Time Kinematic) technology is a more effective positing technology that combined with carrier phase surveying and data transfer and based on the former for real time difference surveying with GPS. It is a brand new step of the development of surveying technology with GPS.Piling positioning can find its significant key role in the first stage during the construction of large bridges and offshore platforms. As the national economy develops, the offshore engineering increases, traditional positioning methods with theodolite or total station have been no longer adapt to precise positioning in the engineering far from coast, while the using of GPS-RTK technology can obtain high efficiency and precision. This paper has discussed the data processing and precision analysis of the results of piling positioning based on GPS-RTK technology, and built the model of it primarily.The results of GPS positioning belong to the World Geodetic System 1984(WGS-84). However, the coordinates of general plane surveying belong to national, local or independent engineering coordinate system, so this paper has discussed various coordinate systems and coordinate transformation among different ones, the coordinate transformation parameters and the influence on precision of piling positioning from coordinate transformation results by builting different two-dimensional and three-dimensional coordinate transformation model. A model considering vertical and cross inclinations condition is put forward to improve the positing accuracy with big rotation angle and three-dimensional coordinate transformation. A case study is cited to achieve that the precision of height can be improved distinctly if the consideration of inclinometer data is involved into the positing model. Some suggestions to calculate the transformation parametersreasonably in engineering projects and configure the hardware of piling positing system have been provided.The software programmed with Matlab correspond to this paper has achieved that the data processing in the offshore piling positioning with RTK more quickly and effectively and the graphic simulation of the process of piling positioning. It is helpful to improve the accuracy of data processing and precision analysis of the result of positioning.In the finality, the problems requiring further studies are discussed briefly.