拉萨城市区域控制网加密及投影转换

Lhasa Urban Area Control Network Encryption and Projecton Conversion

拉萨是中国西藏自治区的首府,也是具有高度民族特色的国际旅游城市。拉萨地处雅鲁藏布江支流拉萨河中游河谷平原,海拔在3 600 m以上。由于拉萨测绘技术条件相对落后,当地坐标系统一直很混乱,为了形成统一的控制框架和为第三次土地调查做好基础工作,故在拉萨市区需要加密以CGCS2000椭球为基础的控制网,并提供与原当地80坐标系的转换七参数。拉萨地处高原区域,为了满足工程测量长度变形不超过1/40000的规定,则要移动中央子午线和选择合适的投影面高度,找到合适施工的平面坐标系。

Lhasa is the capital of the Tibet autonomous region of China,and it is also an international tourist city with high national characteristics. Lhasa is located in the valley plain of the middle reaches of the Lhasa River in the YarlungZangbo River branch,with an altitude of more than 3600 meters above sea level.Because the technical conditions of Lhasa surveying and mapping are relatively backward,the local coordinate system has been very chaotic. In order to form a unified control framework and do the basic work for the third land survey,therefore,it is necessary to encrypt the control network based on the CGCS2000 ellipsoid,and to provide seven parameters of the conversion from the original local 80 coordinate system. Lhasa is located in the plateau area. In order to meet the requirements of engineering survey length and deformation no more than 1/40000,we need to move the central meridian and choose the right projection height,and find the plane coordinate system for proper construction.