顾及高程变化的长距离引水工程投影面选择

Selection of projecting plane in long-distance water diversion project with consideration of elevation variation

在长距离、大范围工程测量中,为控制测距边的投影变形值,常采用设置抵偿投影面的方法,以使测区的长度变形值最小。不同抵偿投影面设置方法均基于测区的高程是恒定不变的假设,而对于高程变化大的测区,长度变形控制则不理想,有的甚至超过规范规定的限差。鉴于此,以滇中引水工程为例,根据投影变形的理论基础,推导出新的抵偿投影面设置方法,该方法是以使测区内长度综合变形最大值达到最小为控制目标,符合规范的要求。通过实例解算,将新方法与现有的理论方法进行对比,结果表明该方法能更好地控制工程长度综合变形的最大值。

In order to control distortion values of projection of ranging edge in the long- distance,large- scale engineering survey,in general,the compensation projecting plane is set to get a minimum- length deformation. The arrangement of various compensation projecting planes are based on constant elevation of survey area; however,the control of length deformation is unsatisfied in the area with large elevation variation,even exceeding the error limit. In view of this,based on the theory of projection distortion,the applicable arrangement of compensation projecting plane is deducted with the case of Dianzhong Water Diversion Project in Yunnan Province. The application of this method meets the related requirements,aiming to minimize the maximum comprehensive length deformation in a survey area. The calculating results show that the method can better control the maximum value of comprehensive length deformation by comparing the new method with current theoretical ones.