长江中游荆江航道整治工程控制测量的投影变形问题的分析和解决

Analyze andSolution of Control Measured Projection Distortion of Jingjiang Channel Regulation Project—the Middle Reaches of the Yangtze River

在对荆江航道整治过程中,现有的控制网不能满足大比例尺的航道整治工程建设,需要重新布设控制网过程,但投影变形过大,设计和施工容易产生误差,不利于航道工程的建设的需要。因此有必要对航道建设中的投影变形进行改正,达到满足航道建设的及测量的规范要求。当长度变形值不大于2.5cm/km时,应采用高斯正形投影统一3°带的平面直角坐标系统。当长度变形值大于2.5cm/km时,采用抵偿高程投影面的方法来消除这种变形。将实地测量的真实边长归算到国家统一的椭球面上,再将椭球面上的边长投影到高斯投影面上。实例分析归算后的长度变形均小于规范要求,可以满足和保证整治工程的施工测量。抵偿高程投影面法既满足方便了资料的统一性,更方便了长江航道数字化航道建设的需要。

In the process for the Jingjiang channel regulation,the existing control network cannot meet the large-scale channel regulation.It need to re-layout control network,but the projection distortion is too large,the design and construction are easy to produce error,which is not conducive to the construction of channel project.Therefore it is necessary to correct the projection distortion in channel construction,to meet measurements regulatory requirements.When the length of the deformation is not greater than 2.5cm/km,it should use Cartesian coordinate system of Gauss conformal projection uniform 3°belt.When the value is greater than 2.5cm/km,projection datum plane with compensation effect is using to eliminate this distortion.The real side of the field measurements is imputed to national unity ellipsoid,and then side of ellipsoid sphere is projected onto the Gaussian projection surface.Deformation length after imputing is less than specification requirements from examples analysis,meeting and assuring the construction measurement of regulation.Projection datum plane with compensation effect meets not only the unity of data,but also the convenient digital channel of the Yangtze River channel construction.