When preparing the main axis of the pay-off project, first, according to the plan and the known point coordinates, quickly calculate the intersection design coordinates of all the main axis coordinates and any intersecting axis, and then start the pay-off.

1) When setting out the main axis of the project with the total station, first set out the outer boundary of the project, enter the polar coordinate setting-out interface of the total station, enter the coordinates of known points 1 to determine the station, look back at the coordinates of known points 2, then enter the coordinates of points to be set out, cooperate with the prism to determine the points to be set out, and repeat the above steps to release the intersection points of axes distributed on the inner and outer boundary lines of the project for connection. However, for oblique boundaries, both ends of oblique lines are laid out in the above way and connected with ink lines. Therefore, the outer boundary part is determined.

According to the external boundary, let out the internal principal axis. Because the height of the building ceiling fluctuates greatly, an off-axis control line of 1 ~ 2m is needed to assist the setting-out of the main axis. Taking the V axis in the plan as an example, as shown in Figure 3, when setting out the main control line, set up polar coordinate lofting according to the coordinates of the known point 1 and the coordinates of the known point 2, and then increase the transverse coordinate values of the intersection of the V axis and the axes 2 and 4 by 1 respectively, and input them into the total station to complete the lofting of one of the main control lines. In this way, all the main control lines in the pile cap can be set out, and then all the main axes can be set out in combination with the distance of the steel ruler.

Fig. 3 V axis in plan view

2) During lofting, 2)RTK technology: set GPS at control point A, set relevant parameters, connect the mobile station receiver, and adjust satellite tracking and ambiguity before lofting. The mobile station converts the calculated coordinate data of the point to be measured into the intersection coordinates of the required axes and inputs them into the manual, and guides the mobile station to move in all directions according to the manual navigation chart until the position of the mobile station coincides with the design point, so that all axes can be marked and set out.

2.3.2 Setting-out of abnormal secondary axis

Due to the large construction scope of this project, the secondary axes of curves and arcs located in the non-load-bearing and secondary load-bearing walls and hollowed-out parts of the first floor of the building are scattered, which increases the difficulty of lofting. In order to ensure the visibility of the total station, the ellipse axis, circular ellipse axis and arc axis in the project are assigned to areas A, B and C3 for independent lofting.