A method and a system for determining a 6-DOF-pose of an object in space use an optical-tracking marker attached to the object. The marker comprises an inner marker area having a circular contour with a known radius and a marker pattern defining at least one characteristic marker feature. A camera image of the marker typically shows an elliptical representation of the circular contour and the marker pattern. Based on the image, parameters describing the elliptical representation are determined and the 6-DOF-pose of the marker in space is derived using the parameters.
