A method, including inserting a flexible probe into a living subject and positioning a distal end of the probe in a heart of the subject, the distal end including a position sensor configured to generate position signals indicative of a position of the distal end, and an electrode configured to convey electrical signals from the heart. The method further includes formulating, in response to the position signals, a first indication of a change in a mean position of the heart within the living subject and deriving a second indication of a change in the electrical signals. The method also includes determining, in response to the first and second indications, a new mean position of the heart.