The engineer can hold the instrument and move it flexibly to determine the spatial position of the scanner during the scanning process through visual markers, so as to complete the overall reconstruction of the 3D point cloud on the surface of the object. The measuring instrument can be easily carried to an industrial site or a good production workshop, and can perform efficient and accurate scanning according to the size and shape of the scanned object. The operation process is flexible and convenient, and it can be used in various complex application scenarios.