Integrated calibration of a 3D attitude sensor in large-scale metrology

A novel calibration method is presented for a sensor fusion system in large-scale metrology, which improves the calibration efficiency and reliability. The attitude sensor is composed of a pinhole prism, a converging lens, an area-array camera and a biaxial inclinometer. A mathematical model is established to determine its three-dimensional attitude relative to a cooperative total station by using two vector observations from the imaging system and the inclinometer. The measurement model developed has two aspects to be calibrated: the intrinsic parameters of the imaging model; and the transformation matrix between the camera and the inclinometer. An integrated calibration method using a three-axis rotary table and a total station is then proposed. A single mounting position of the attitude sensor on the rotary table is sufficient to solve for all parameters of the measurement model. A correction technique for the reference laser beam of the total station removes the need for accurate positioning of the sensor on the rotary table. Calibration measurements are made at multiple angular positions of the rotary table in order to determine all the unknown parameters in the model. Experimental verification has verified the practicality and accuracy of this calibration method. Results show that the mean deviations of attitude angles using the proposed method are less than 0.01°.