A method includes, identifying, in a three-dimensional (3D) anatomical image of a patient organ, multiple anatomical points corresponding to respective predefined locations on a skin of the patient organ in a first coordinate system. Multiple positions in a second coordinate system, measured by a position sensor of a position-tracking system at the respective predefined locations on the skin of the patient organ, are received. At each predefined location, a distance is calculated between a respective anatomical point and closest bone tissue of the patient organ. Weights are assigned to the predefined locations based on respective distances between the anatomical points and the closest bone tissue. The first and second coordinate systems are registered, by correlating between the positions and the respective anatomical points using the assigned weights.
