A visual compass based on SLAM

Accurate full 3 axis orientation is computed using a low cost calibrated camera. We present a simultaneous sensor location and mapping method that uses a purely rotating camera as sensor and distant points, ideally at infinity, as features. A smooth constant angular velocity pure rotation motion model codifies the camera location. Because of the sequential EKF approach used, and the number of features in the map, about a hundred, the proposed method has been implemented in real time at standard video rates. Experimental results with real images show that the system is able to close loops with 360deg pan and 360deg cyclotorsion rotations. Sequences show good performance under challenging conditions: hand-held camera, varying natural outdoor illumination, low cost camera and lens and people moving in the scene