[Visitor (58.214.*.*)]answers [Chinese ]  Time :20201010  The tunnel construction coordinate system can adopt the geodetic coordinate system or * coordinate system. The geodetic coordinate system commonly used in China is Xi'an 80 or 2000, which can use the same coordinate system as other projects. Convenient for joint test management. Of course, the tunnel* coordinate system can also be used, usually the tunnel axis is the X coordinate and the offset direction is the Y coordinate, which can directly guide the tunnel mileage and offset value. The geodetic coordinate system is a coordinate system established on the reference ellipsoid in geodetic surveying. The position of the ground point is expressed by the longitude of the earth, the latitude of the earth and the height of the earth. The establishment of the geodetic coordinate system includes selecting an ellipsoid, performing a * on the ellipsoid, and determining a geodetic calculation*. An earth ellipsoid whose shape, size, and orientation have been determined is called a reference ellipsoid. Once the reference ellipsoid is determined, it indicates that the geodetic coordinate system has been established. The geodetic coordinate system is a geographic coordinate system. The geodetic coordinate system is righthanded. 
