Automatic elevator shaft measurement with mobile measurement device based on 3D positioning

In the construction of high-rise buildings, measuring elevator shaft is dangerous and physically burdensome to the workers because the dimensions of the main structure are measured by hand at all floor openings using the plumb line, which is the standard for the inside of the shaft, as the reference position. This paper proposes an automatic measurement method that can measure the dimensions of the main structure of the shaft with high accuracy. This method uses a mobile measuring device lifted by a winch. The measuring device do self-positioning with a pair of positioners that calculate the absolute position of the device from two vertical laser beams, a distance sensor for height measurement, an inclination senor for tilt compensation. It detects the main structure of elevator shaft by camera and order the winch to lift it to exact height to measure the structure. It measures the main structure with a horizontal distance measuring unit consisting of a rotary stage and two laser rangefinders. Then, three-dimensional data of the main structure of the shaft can be obtained by merging self-positioning information with horizontal measuring data. To evaluate the usefulness of this system, an automatic measurement test was performed on a shaft with a height of 23 m. The recognition period of the camera is 5 Hz, and it was confirmed that it can be automatically stationary at the height of the main structure. In addition, the maximum error in the repeated measurement of the specific point specified in the main structure was ± 4.4 mm, which was less than the ± 5 mm required for the elevator shaft measurement.