[en] Highlights: • The paper deals with the treatment of possible symmetry-breaking elements. • The paper takes advantage of the signals from the magnetic diagnostic system. • The paper proposes a procedure to filter the effect of displacements. • The proposed procedure identifies the amplitude of shift and tilt deformations. - Abstract: Plasma equilibria can be altered by symmetry-breaking elements in vessel and first wall geometry. Also diagnostic systems fastened to vessel or mechanical supporting structures are influenced by the lack of symmetry of such structures, as a matter of fact they leave their nominal position measuring the field in the actual displaced position. Real time plasma position and shape identification are mainly based on magnetic measurements. A suitable treatment of the measuring signal can provide effective information about the actual probe positions. The paper deals with this problem, introducing, to describe the actual probes position, a description base for possible 3D geometries characterized by small deformations with respect to nominal (axially-symmetric) configuration, examples being shifts or rotations along orthogonal axes. As a side result, information about possible deformations of the geometry is obtained.