Sea buoys served an effective tool within tsunami warning systems in the Great East Japan Earthquake. Currently, merchant ships and sea buoys must be equipped with GPS systems. If ships in the anchorage are allowed to function as sea buoys, it will be possible to increase observation points. Furthermore, more extensive and accurate analysis of sea state can be expected. However, ships cannot always obtain signals from reference stations because these navigation areas are quite different. In this paper, we focused on Precise Point Positioning (PPP) on ships. Efforts toward using ships as alternatives to sea buoys do not exist in previous researches. Our purpose is to verify the performance when the ship is anchoring and consider new utilization of PPP. We compared the performance of PPP from both the fixed point of land and the ship in the anchorage. Experimental results showed that it was possible to determine positioning with accuracy at approximately 2cm (standard deviation) in horizontal direction and at approximately 5cm (standard deviation) in vertical direction when the ship was anchoring. However, RMS error was observed approximately 20cm at maximum between PPP and RTK fixed solutions. Moreover, we proposed disaster preventing systems using ships in the anchorage instead of sea buoys and applying PPP.
