What is the definition of plumb line?

The definition of plumb line in civil engineering is as follows: the connecting line between the center of gravity of an object and the center of gravity of the earth is called plumb line (measured by cone plumb hammer). Mostly used in architectural survey. Tie a heavy object with one end of a string. When it is stationary relative to the ground, the straight line where the rope is located is the plumb line, also called the heavy plumb line.

Gravity direction line in the earth's gravity field. It is perpendicular to the horizon and is the reference line for field observation. The direction of the hanging weight when hanging freely is the direction of this line. The plane containing it is called a vertical plane.

Extended data:

The plumb line is an instrument made by using the principle that the line or plane parallel to the plumb line is vertical and the line or plane perpendicular to the plumb line is horizontal when the heavy object is at rest.

1, if the gravity direction is always vertical downward, if the plumb line is parallel to the wall, the wall is vertical;

2. If the gravity direction is always vertical downward and the plumb line is vertical to the horizontal plane, it means that the window sill is horizontal.

In addition, the change of plumb line is an unsolved problem in astronomy and geodesy. Ground optical astronomical observation is based on the vertical line where the instrument is located. If there is an uncorrected change in the plumb line, it is necessary to further correct the influence of this change on all previous measurement results.

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