The authors present the results of studying the accuracy of determining the horizontal displacements of the deformation mark through the polar method from a spot, whose position, in turn, is defined with a total station by an inverse angular serif or the same linear-angular one to the points of the reference network. The covariance matrices of the deformation mark’s coordinate vector and the surveying point for both serifs are obtained and their elements are studied both with and without taking the errors of the initial data into account. The mentioned point’s position errors obtained through the corresponding elements of the covariance matrix coincided with the control calculations performed using the known formulas of back serifs. At the same time, the value of the deformation mark’s position error is greater than the sum of those of surveying point’s and the polar serif on the deformation mark, due to the influence of errors of the initial directional angle.