This paper presents an inertial navigation system aided by local ranging measurements derived from an ultrawideband system. The system consists of one onboard tag and several onshore anchors. It is motivated by the need to complement satellite systems in harbor areas to reduce the risk of localization dropout during high precision closedloop maneuvering and docking of ships as it may imply severe consequences. The proposed state estimation algorithm includes ranging bias to compensate for minor inaccuracies originating mostly from tag and anchor processing time.The complete ultra-wideband aided inertial navigation system is validated using full-scale measurements collected during multiple dockings of a passenger ferry in Trondheim, Norway. The results show that the proposed localization system has comparable performance to state-of-the art inertial navigation systems aided by real-time kinematic satellite position measurements. Thus, it offers a viable alternative and complement which may contribute to safe and efficient high precision closed-loop maneuvering and docking of marine vessels.