There are many pay-off methods in the field operation of construction pay-off; Generally, there are two pay-off methods: measuring pay-off with gantry positioning ruler and measuring pay-off. The former piles the vertical dragon door panel at a certain distance around the foundation of the building to be set out, draws a large line at right angles to the construction line on the gantry plate, tightens the line as much as possible, and then uses the Pythagorean theorem to combine steel rulers with larger sizes, generally 6, 8, 10m, which is more accurate. First, measure the dimensions of the two control lines and mark them with a red pencil. Then, two people pull the ruler and one person swings it. Then fix the construction line on the gantry and proofread it from the beginning with a steel ruler. After confirmation, hang lines around and check with steel ruler. According to the size of the axis on the drawing, measure the setting point with a ruler, hang it vertically on the ground, put the excavation lines with lime powder respectively, measure the control elevation with a level, and put it on the gantry.

If the latter can use theodolite or total station, it will be much simpler. As long as the control points are known on the drawings or determined on site, the specific position of the axis can be determined according to the distance and angle relationship on the drawings.

Specifically:

1. Generally speaking, the steel plate is embedded in the pre-selected internal control point position, and it is convenient to find the intersection point on the steel plate with theodolite as the base point of the vertical shaft, and then hang it with a sledgehammer. Align the point of the hammer with the base point of the shaft. When the hammer is aimed at the base point, inform the floor personnel to use the walkie-talkie for positioning. When lowering the hanging hammer, the checking personnel should observe the point difference between the tip of the hanging hammer and the steel plate from two mutually perpendicular directions, and inform the upstairs personnel to adjust the position in the steel wire line in time. When the hammer tip and the cross overlap from both sides, the upper fixing point can be notified.

As for the elasticity of steel wire, it does exist. The key is that the pay-off wheel on the floor should be specially made, the height can be adjusted slightly, and the lock is reliable, so that the pay-off is more convenient.

2. Because of the high-rise floors and external scaffolding, the line hammer method and external control method are not applicable, and the endoscopic method can be used. That is, two reserved holes are left at the same position on each floor, and the axis of the next floor is led up through these two holes. If you leave three holes, you can use a theodolite, and only a wire hammer and a steel rule can complete the setting-out.

3. The outer space method is adopted below 0.000, that is, the control piles are laid and the axis is measured by theodolite. Above 0.000, the internal control method is adopted, that is, the control axis is measured by theodolite on the first floor plane, the steel plate is embedded where visibility can be achieved on the first floor plane, and the intersection point and notch are found on the steel plate by theodolite as the basic points for longitudinal axis measurement. Then measure the N-layer axis upward from this point with a plumb instrument. Internal control method is commonly used in lofting of high-rise buildings. Specifically, it is to find a suitable distance parallel to the axis near the building axis. Our class will find a location about 1 m to bury the steel plate, find the intersection point and notch on the steel plate as the basic point of vertical axis retest, and then use plumb bob instrument or laser theodolite to retest the N-layer axis upward from this point. For example, you are now surveying from the first floor to the second floor. You aim at the point on the first floor and hit it with a laser theodolite. On the second floor, just catch the point coming from below with glass. Then measure 1 m from this point on the second floor, which is the location of the building axis.