A Motion Correction Technique for Laser Scanning of Moving Objects

Abstract

The fundamental limitation for laser scanning of an object is that the object should be stationary. In this letter, we propose a novel technique for obtaining 3-D point cloud of a moving object by applying motion correction, so that the point cloud is correct in relative and absolute sense, and represents the true shape of the scanned object. In the proposed technique, a laser scanner is used to scan an object which is mounted with a GPS/IMU system and stationed at a distance from the scanner. The object is put in continuous motion (in a limited area) which may be linear, nonlinear, rotational, or of random type. The point cloud collected by the laser scanner is combined with the position and orientation information of the moving object to transform the whole point cloud into a new coordinate system, called object body coordinate system (OBCS), which is fixed to the object. This is realized, first by determining the relationship between an inertial measurement unit (IMU)body coordinate system and the OBCS, and then by using this relation to convert the coordinates of object measured in global coordinate system through laser scanner into the OBCS. Prior to this, the laser scanner is oriented to measure coordinates in global coordinate system. This letter first presents a complete theoretical background of the proposed method for a general case, and then outlines some simplified cases as encountered in practice. The proposed technique has applications in scanning objects that are not stable, e.g., a ship in a harbor.