The locus of points in space described by the superposition of two fields having different directions and whose variations in time are of the form Acos(ωt) and Bcos(ωt+θ). In electromagnetic prospecting, neither the direction nor the phase of the primary and secondary fields are the same so that the superposition of the two fields results in elliptical polarization. For the ellipse shown in Figure P-7, the modulus of the magnetic wavetilt is given by |Hz|/|Hx|, the tilt angle or pitch by α, and the ellipticity by |H2|/|H1|. Ellipticity is positive or negative as the vector rotates clockwise or counterclockwise. See Smith and Ward (1974).