Disclosed here are methods and systems that relate to determining a moving direction of a mobile device user. The methods and systems relate to using an inertial navigation system such as an accelerometer and gyroscope to aid in the determination of the moving direction of the user. The methods and systems may receive an acceleration reading associated with the mobile device, and determine a step frequency of the user based on the acceleration reading. The methods and systems may determine a theoretical model to fit the acceleration reading, and may determine the moving direction of the user based on the theoretical model.