Embodiments of the present disclosure generally provide systems and methods for connecting a power supply of a tow vehicle to a trailer. The all-road updating data is a difference of all roads extracted from an all-road map data, and the main-road updating map data is a difference of specified roads extracted from the all-road map data. In addition, a user equipment is provided and includes a detection unit configured to detect a current screen direction in real time; and a setting unit configured to place a system visual key in currently displayed title bar of the user equipment when the detection unit determining an occurrence of a change of the current screen direction. A list of potential connections between at least selected ones of the sources is provided.