基于CGCS2000椭球的遂宁市独立坐标系的建立与优化探讨

Discussion on Establishment and Optimization of Suining Independent Coordinate System Based on CGCS2000 Ellipsoid

现行国家相关规范中,规定了在城市测量中使用的平面坐标系统其投影长度变形值不应大于25 mm/km,但在高海拔地方,以及距中心子午线位置较远的地区使用标准的国家坐标系时,却往往会出现长度投影变形值超过限差要求的情况。为了满足国家规范的限差要求,我们通常采用移动中央子午线或变动高程投影面的方式,去削弱高斯投影和高程归算带来的边长长度投影变形,从而建立城市独立坐标系。本文详细介绍了长度投影变形的原因、建立独立坐标系的必要性和方法,以及如何结合遂宁市的地理位置和平均高程的具体情况,利用投影变形公式去选择确定城市独立坐标系的各个参数,并对现有的遂宁独立坐标系的投影面参数提出了优化建议。

In the current national regulations,it is stipulated that the projected length deformation value of the plane coordinate system used in urban survey should not be greater than 25mm/km.However,when the standard national coordinate system is used at high altitude or far from the central meridian,the projected length deformation value often exceeds the requirement of the margin.In order to meet the requirements of the national standard,we usually adopt the way of moving the central meridian or changing the elevation projection surface to weaken the side length projection deformation caused by Gaussian projection and elevation reduction,so as to establish the independent urban coordinate system.Length projection deformation is introduced in detail in this paper,the necessity of establishing independent coordinate system and the cause of method,as well as how to combine the suining city location and the average elevation of specific circumstances,to choose projection deformation formula is used to determine the city all parameters of the independent coordinate system,and the existing independent coordinate system in Suining,illustrating the parameters optimization suggestions were put forward.