A self-aligning interface for interfacing; an extendable conveyor attached to a floor of a warehouse to a robotic carton unloader unloading cartons within a semi-trailer, the extendable conveyor has an extendable nose conveyor to receive unloaded cartons thereon from the robotic carton unloader during the unloading process, the self-aligning interface comprising: a positional measurement device (6320, 6320b, 6320c) mounted on the robotic carton unloader and operatively engaged with the extendable conveyor to provide positional information about the location of the extendable nose conveyor relative to the positional measurement device (6320, 6320b, 6320c); and a control unit attached to the robotic carton unloader for robotic control of the robotic carton unloader and the unloading process, the control unit operably connected to the positional measurement device (6320, 6320b, 6320c) and communicably connected to the extendable conveyor, the control unit using the positional information to calculate and control extension and retraction movements of the extendable conveyor to move in unison with the forward and reverse movements of the robotic carton unloader; characterized in that the positional measurement device (6320, 6320b, 6320c) comprises a retractable cable connected to the extendable nose conveyor with attachment member to sense distance and angular differences between the positional measurement device (6320, 6320b, 6320c) and the connection to the extendable nose conveyor, and in that the retractable cable is operatively coupled to one or more encoders (6338, 6360, 6390) for measuring extension and retraction distances and vertical and horizontal angles of the retractable cable relative to the positional measurement device (6320, 6320b, 6320c). a positional measurement device (6320, 6320b, 6320c) mounted on the robotic carton unloader and operatively engaged with the extendable conveyor to provide positional information about the location of the extendable nose conveyor relative to the positional measurement device (6320, 6320b, 6320c); and a control unit attached to the robotic carton unloader for robotic control of the robotic carton unloader and the unloading process, the control unit operably connected to the positional measurement device (6320, 6320b, 6320c) and communicably connected to the extendable conveyor, the control unit using the positional information to calculate and control extension and retraction movements of the extendable conveyor to move in unison with the forward and reverse movements of the robotic carton unloader; characterized in that the positional measurement device (6320, 6320b, 6320c) comprises a retractable cable connected to the extendable nose conveyor with attachment member to sense distance and angular differences between the positional measurement device (6320, 6320b, 6320c) and the connection to the extendable nose conveyor, and in that the retractable cable is operatively coupled to one or more encoders (6338, 6360, 6390) for measuring extension and retraction distances and vertical and horizontal angles of the retractable cable relative to the positional measurement device (6320, 6320b, 6320c). the positional measurement device (6320, 6320b, 6320c) comprises a retractable cable connected to the extendable nose conveyor with attachment member to sense distance and angular differences between the positional measurement device (6320, 6320b, 6320c) and the connection to the extendable nose conveyor, and in that the retractable cable is operatively coupled to one or more encoders (6338, 6360, 6390) for measuring extension and retraction distances and vertical and horizontal angles of the retractable cable relative to the positional measurement device (6320, 6320b, 6320c).