A method and an apparatus are provided for determining an orientation of a tool with respect to a reference direction. The tool is configured to be moved along a wellbore and to generate information usable to determine an orientation of the tool. At least one first signal is indicative of an orientation of a directional reference system with respect to the reference direction. Information regarding a relative orientation of the tool with respect to the directional reference system is used to determine the orientation of the tool with respect to the reference direction in response at least in part to the at least one first signal.