The error ellipse provides the orientation of the largest error at a given station in a horizontal adjustment. As given in Chapter 19 of Adjustment Computations: Spatial Data Analysis, it is computed from the 2 by 2 submatrix that defines the unknowns for the station in question. The process of transforming the original submatrix to the matrix used to compute the error ellipse is known as orthogonalization. In mathematics this process produces eignevalues and eigenvectors. This worksheet demonstrates the process of computing error ellipses using the method presented in the textbook and eigenvalues.