引大济岷工程分段抵偿投影面和投影带的合理选择

Reasonable Selection of Sectional Compensation Projection Surface and Belt for Dadu-Minjiang Water Diversion Project

在建立大型水利工程GPS控制网的内业处理过程中,为满足地形测图和已有地形图利用的精度要求,降低高斯投影变形和高程面投影变形对平差成果的影响,经常会在水利测绘中采用分段投影的方法。其中,测区抵偿高程面和移动中央子午线的选择是最困难的工作。本文对引大济岷工程GPS控制网的分段投影计算进行了简单剖析。分析结果表明:选取分段测区平均高程来做投影抵偿高程面,有利于测区投影变形均匀,从而使测区投影长度的变形值不大于规定值。

In order to meet the accuracy requirements of topographic mapping and existed topographic maps,and reduce the influence of Gauss projection deformation and elevation surface projection deformation on adjustment results,the piecewise projection method is often used in the indoor processing of the large-scale hydraulic engineering of GPS control network.Among which,the selection of the offset elevation surface and moving central meridian in the measuring region is the most difficult work.This paper briefly analyzes the piecewise projection calculation of the GPS control network of the Dadu-Minjiang water diversion project.The analysis results show that to take the average elevation in the measuring region as the compensation projection elevation surface is beneficial to the uniform projection deformation in the measuring region and the projection length deformation value in the measuring region is not greater than the specified value.