The Application of “Marine Engineering GPS Piling and Positioning System” in the Compensation Elevation Plane Projection Coordinate System

Pile sinking positioning is an important technical link in marine engineering construction. In order to meet the needs of the development of offshore engineering construction, our unit has taken the lead in developing the “Marine Engineering GPS Piling Positioning System” that serves various types of offshore engineering pile sinking positioning in China. The basic principle of pile sinking positioning is to first use RTK GPS (including GNSS, the same below) as a positioning and orientation instrument to locate and orient the pile driving vessel. On this basis, a distance measuring instrument is used to accurately position the pile driving. The system has high positioning accuracy and greatly improves construction efficiency. The “Marine Engineering GPS Piling and Positioning System” currently has functions that fully meet the conversion of RTK GPS output geodetic coordinates to national coordinate systems or various planar coordinate systems established through normal Gaussian projection. However, the conversion function for some planar coordinate systems established through special methods has not yet been realized. The pile sinking project of Wenzhou Liquefied Natural Gas (LNG) Terminal Supporting Terminal Project adopts a plane coordinate system of − 850 m as the compensation surface to compensate for the projection deformation directly generated by the Gaussian projection. The “Marine Engineering GPS Pile Driving Positioning System” cannot directly convert the geo-detic coordinates output by RTK GPS to the plane coordinate system of the compensation surface. This article takes the project as an example and establishes a new plane coordinate system using the projection strip replacement calculation method. On the premise of ensuring that the projection deformation of the new and old coordinate systems in the construction area meets the requirements, the transformation relationship between the new and old coordinate systems is obtained to convert the coordinates of the old coordinate systems. The new coordinate system is applied to the “Marine Engineering GPS Piling and Positioning System”, to successfully overcome the problem of the positioning system not being able to directly use the coordinate system on the compensation surface, and successfully complete the pile sinking positioning task of the project.