Exact image theory for the vertically layered ground, previously introduced by the second author and collaborators, is simplified through the equivalent source concept. In particular, the image for a horizontal source can be derived by replacing the source by an equivalent vertical source and applying simpler theory for the vertical source. The resulting vertical image, again, can be replaced by an equivalent horizontal image. The equivalent source method circumvents the more complicated dyadic analysis applied previously. The layered half space may have any isotropic or bi-isotropic structure represented by four reflection operators. As an example, image expressions are derived for the horizontal dipole above a slightly chiral half space, applying the theory derived previously for the vertical electric and magnetic dipoles.