A navigation system includes an in-vehicle portion and a removable navigational unit, where the removable navigation unit is a portable device with navigation capability on its own. The removable navigation unit is capable of being connected to the in-vehicle portion through an navigation interface to perform the navigation function in combination with the in-vehicle portion. The removable navigation unit seamlessly integrates with the in-vehicle portion of the vehicle to provide portability of navigation function when used independently from the in-vehicle portion, and taking advantage of the components of in-vehicle portion when used in conjunction with the in-vehicle portion.