A robust direct linear transformation for camera pose estimation using points

Camera pose estimation from 3D points and their 2D projections, known as the perspective-n-point (PnP) problem, is a fundamental task in computer vision. In this paper, we propose a robust direct linear transformation method for the PnP problem. The novelty lies in that a plane constraint based on the pinhole camera model is introduced, and an over-constrained linear equation system is obtained by merging the linear form of both the measured point correspondences and the plane constraint. As a result, our method successfully reduces the minimal number of point correspondences required by the linear solver to 4, and yields a unique solution for 4-point, 5-point, and n-point pose estimation. Experiment results, using both synthetic and real data, show that our method is substantially faster, and offers the accuracy and precision comparable with that of state-of-the-art methods.