Abstract: A method and apparatus for determining a current speed of a wrist-worn mobile electronic device. In some configurations, a wrist-worn mobile electronic device is provided that includes a motion sensor configured to sense motion of the user's wrist and generate acceleration data, a position determining module, a non-transitory memory configured to store scale factors corresponding to a plurality of average acceleration points, and a processor operable to determine a cadence for the user, an average acceleration of the user's wrist, select a scale factor and compute a current speed for the mobile electronic device based on the cadence, determined average acceleration and selected scale factor.