Chang will continue studies on the statistical properties of estimated rotation matrices. An important application is the determination of the errors in the reconstructions of the past positions of tectonic plates (known popularly as "continental drift"). He analyzes the spherical regression model for the shift from one point to another on the surface of the unit sphere: multiplication by an orthogonal rotation matrix A is followed by the addition of a random error. For different points the rotation matrix A remains the same but the error is symmetrically distributed around the corresponding rotated point. Robust extensions of this model will be studied.
