The device e.g. catheter(10), has a transmitter (11) emitting an electromagnetic signal. The electromagnetic signal is adapted to propagate with a wavelength in a body, so that the electromagnetic signal in three positions (18) is detectable by a receiver (19) for tracking variations of a position of the transmitter relative to the receiver. The wavelength is selected so that a distance from each transmitter to each of the three positions is within the same integer number of wavelengths of the electromagnetic signal. An independent claim is also included for a system for tracking a position of a target area inside a body.
