We present a method for measuring the three-dimensional orientation of planar surfaces. We derive a model relating the spatially varying instantaneous frequency of the image texture to the instantaneous frequency of the surface texture, to the orientation of the surface, and to the parameters of the imaging system. We measure the localized frequency at each image point with Gabor wavelets and use it to solve for the surface orientation according to the model. The method does not require the extraction of discrete texture elements. The algorithm has a mean error of about 5 degrees in the measured slant and tilt on a test set of 12 real-world surfaces.