The invention relates to method and a system of interpreting angular orientation data. It is determined, whether the angular deviation of a current angular orientation (C) of a sensor device (12) from a last extreme angular orientation (L) currently decreases after having increased before up to a provisional new extreme angular orientation (P), thereby determining that the provisional new extreme angular orientation (P) is a new extreme angular orientation. Information relating to a new extreme angular orientation, such as an angular range of motion, may be output to a user.