A gaze tracking device (120) is calibrated to a display unit (110)by presenting graphical guide objects (G1, G2, G3) on an activearea (110A) thereof, which designate distinctive features (121,122； 123) reflecting how the device (120) may be positioned (x1,x2) on a first side (110X) of a frame (110F) of the display unit(110). User commands (MC) move the objects (G1, G2, G3) onthe display's active area (110A) in a first direction parallel to thefirst side (110X) of the frame (110F). A position value (Px) designatingan actual position for the gaze tracking device (120)on the first side (110X) of the frame (110F) is assigned basedon a current position of the graphical guide objects (G1, G2, G3)on the active area (110A). An offset value (X-OFF) is calculatedbased on the assigned position value (Px) and a known measureof the active area (110A). The offset value represents a distancein the first direction between a well-defined point (123) of thegaze tracking device (120) and a well-defined point of the firstside (110X). Width and height measures (X, Y) reflecting aphysical extension of the active area (110A) are also determinedand stored in response to a user input confirmation command(CC) together with the offset value (X-OFF), so that the valuescan be used when determining a user's gaze point on the activearea (110A).
