Abstract: A method and apparatus for determining fatigue/surface crack features on metal surfaces is disclosed wherein the cracks may be empty, filled, or covered with a dielectric (e.g., paint). The present invention includes a microwave waveguide having an aperture for scanning over a surface and thereby characterizing changes in a standing wave within the waveguide when a crack is scanned. In particular, crack related data resulting from standing wave perturbations can be analyzed for determining crack geometric features such as crack width, crack depth, crack length and crack tips. These features are determinable with high precision in comparison to the size of the aperture. When locating and/or sizing the geometric features of a crack, voltage changes induced by higher order modes generated by various orientations of the crack in relation to the aperture are utilized for generating the crack related data.