高海拔地区铁路施工控制网的建立

The Building of Railway Construction Control Network in the High Altitude Area

研究目的:在高海拔地区的铁路控制测量中,控制网的边长将产生较大的长度投影变形,在这个区域如果采用国家坐标系建立控制网,其长度变形不能满足铁路施工控制网精度要求,这会对线路施工放样及隧道贯通测量等工作造成比较大的影响。因此合理评价及处理长度投影变形对坐标成果的影响,建立适合高海拔地区的铁路施工控制网,已成为这个区域工程控制测量的一项重要内容。研究结论:在高海拔地区铁路施工控制测量中,长度变形主要是以高程归算变形为主,所以选择"抵偿高程面"作为投影面,按正形投影3°带建立独立坐标系应该是最佳选择。该方法换算简便,而且换系后的新坐标与原国家统一坐标系的坐标十分接近,有利于测区内外之间的联系。如果线路东西向跨度比较大,而且测区中心离中央子午线比较远时,应该考虑"选择任意投影带"或其它方法。

Research purposes： In the railway control surveying of the high - altitude areas, the side of control network will have a greater length of the projection length distortion. If the control network is established over the national coordinates in the region, the deformation of the length of the railway construction can not meet the requirements of precision control network, which will have a great effect on the coordinates stakeout of line construction survey and breakthrough measurement. Therefore, a reasonable length of the evaluation and treatment of deformed projection of the results of coordinates, and the establishment of high - altitude areas to control the construction of the railway network has become an important part of engineering control surveying in the area. Research conclusions： In the high altitude control surveying of the railway construction, distortion of reductions of elevation is mainly in the length deformation. So, it is the best choice to select the level surface with compensation used as plane of projection ,and build an independent coordinates system based on the orthomorphic projection 3~bands. The method is simple conversion, furthermore, the result of calculated coordinates is very close to the coordinates in the original coordinate system of national unity. It is helpful for the link between inside and outside of the surveying area. If the line length has a wide span from east to west, and when the center of the surveying area is far from the central meridian, we should consider selecting ＂any local projective stripes＂ or other methods.