In this article we discuss the 2D-3D pose estimation problem of 3D free-form surface models. In our scenario we observe free-form surface models in an image of a calibrated camera. Pose estimation means to estimate the relative position and orientation of the 3D object to the reference camera system. The object itself is modelled as a twoparametric surface model which is represented by Fourier descriptors. It enables a low-pass description of the surface model, which is advantageously applied to the pose problem. To achieve the combination of such a signal-based model within the geometry of the pose scenario, the conformal geometric algebra is used and applied.