Mutual Localization: Two Camera Relative 6-DOF Pose Estimation from Reciprocal Fiducial Observation

Concurrently estimating the 6-DOF pose of multiple cameras or robots---cooperative localization---is a core problem in contemporary robotics. Current works focus on a set of mutually observable world landmarks and often require inbuilt egomotion estimates; situations in which both assumptions are violated often arise. In contrast to these existing works in cooperative localization, we propose a cooperative localization method, which we call mutual localization, that uses reciprocal observations of camera-fiducials to obviate the need for egomotion estimates and mutually observable world landmarks. We derive and solve an algebraic formulation for the pose of the two camera mutual localization setup under these assumptions. Our experiments demonstrate the capabilities of our proposal egomotion-free cooperative localization method: for example, the method achieves 1cm range and 0.05 degree accuracy at 2m sensing for 6-DOF pose. To demonstrate the applicability of the proposed work, we use the proposed mutual localization techniques in 3D metric reconstruction by a pair of cameras with fiducial markers affixed.