  This paper is concerned with the electromagnetic inverse scattering problem
that aims to determine the location and shape of anisotropic scatterers from
far field data (at a fixed frequency). We study the orthogonality sampling
method which is a simple, fast and robust imaging method for solving the
electromagnetic inverse shape problem. We first provide a theoretical
foundation for the sampling method and a resolution analysis of its imaging
functional. We then establish an equivalent relation between the orthogonality
sampling method and direct sampling method as well as resolution analysis for
the latter. The analysis used to justify the Factorization method for the far
field operator plays an important role in the justifications. Finally, we
present some numerical examples to validate the performance of the sampling
methods for anisotropic scatterers in three dimensions.
