A portable apparatus including a first interface configured to input speed data of a user or location data of the user from a positioning unit utilizing external reference points is disclosed. The portable apparatus also includes a second interface configured to input motion data of a user from a self-contained activity determining unit. Furthermore, the portable apparatus includes a processing unit configured to constitute, if the first interface only inputs the location data, speed data from the location data, select filtering characteristics based on the motion data, filter the speed data with the selected filtering characteristics, and determine physiological data of the user with the filtered speed data.