A device and method of determining a travel direction of a mobile device carried by a user are disclosed. The method includes determining a line along which the mobile device is traveling, where the determining may be based on sensed acceleration of the mobile device. A walking style of the user traveling with the mobile device may be determined. The sensed acceleration may be resolved into at least two mutually perpendicular components. A first component may be substantially parallel with gravity, and a second component may be orthogonal to the first component. The travel direction of the mobile device along the travel line may be determined based on a user's walking style and the resolved sensed acceleration. The determining of the line may include applying a linear least square fitting method to a plurality of acceleration readings obtained from at least one inertial navigation sensor.