We use Fourier descriptors (FD's) to represent shape in model-based pose estimation. Specific invariance and
normalization requirements for shape descriptors concerning to pose estimation are proposed. FD's are improved to meet
such requirements. Common issues and techniques for such application are focused on. Starting point of the shape
contour is fixed to the upper left corner point. Distance pairs instead of edge coordinate pairs recast the shape sequence.
Moving average filtering is proceeded to remove the noises of the shape sequence. Shape sequence is re-sampled to
make it definite length. FD's amplitude is normalized to the range of 0 to 1. Variance of sequences between observed
and library FD's is defined as the shape matching objective function. For simulation, we use a missile model of
Milkshape3d format. Results show that by adopting the improved FD's, we can arrive at a pose estimation practically by
randomly optimal search of library FD's.