Abstract: During digitalized joining procedure of large-scale parts, the iGPS is more and more used as
measuring equipment for 3D coordinates. Based on the features of iGPS-measured-data, a
unit-quaternion-based attitude matching algorithm is proposed. Compared to other existing attitude
matching methods, this algorithm is simpler and more concise in calculation, and thus more effective in
programming. Correspondent verification tests and error calculation indicate the accuracy of this
algorithm for large rotation angles.

Key words: iGPS, attitude matching, unit quaternion, coordinate transformation