“海工工程GPS打桩定位系统”在抵偿高程面投影坐标系中的应用

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

摘要: 沉桩定位是海工工程建设中的重要技术环节。为适应海上工程建设发展的需要，我单位在国内率先研发了服务于各类海工工程沉桩定位的“海工工程GPS打桩定位系统”。其沉桩定位的基本原理是，首先以RTK GPS (包括GNSS，下同)作为定位和定向仪器对打桩船进行定位定向，在此基础上，再采用测距仪对施打桩进行精确定位，系统定位精度高，同时大大提高了施工效率。“海工工程GPS打桩定位系统”目前已有功能完全满足将RTK GPS输出的大地坐标向国家坐标系或各类通过正常的高斯投影建立的平面坐标系的转换，但对一些通过特殊方法建立的平面坐标系的转换功能尚未实现。温州液化天然气(LNG)接收站配套码头工程沉桩工程，设计采用了−850 m作为抵偿面的平面坐标系统，以抵偿直接采用该高斯投影产生的投影形变，“海工工程GPS打桩定位系统”无法直接将RTK GPS输出的大地坐标转换到该抵偿面的平面坐标系统。本文以该项目为例，采用投影换带计算方法建立新的平面坐标系统，并在保证新旧坐标系统在施工区域内投影形变满足要求的前提下，求取新旧坐标系的转换关系对旧坐标系坐标进行转换，将新坐标系统应用到“海工工程GPS打桩定位系统”中，成功克服了定位系统无法直接采用高程抵偿面上的坐标系统的问题，成功完成了项目的沉桩定位任务。

Abstract: 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 posi-tioning is to first use RTK GPS (including GNSS, the same below) as a positioning and orientation in-strument 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” cur-rently has functions that fully meet the conversion of RTK GPS output geodetic coordinates to na-tional coordinate systems or various planar coordinate systems established through normal Gauss-ian 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 di-rectly convert the geodetic 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 co-ordinate system using the projection strip replacement calculation method. On the premise of en-suring 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 sys-tem on the compensation surface, and successfully complete the pile sinking positioning task of the project.