In recent years, more accurate wave data base representing ocean wave environment used for planning for construction of ship and floating offshore structure is demanded. For this purpose, it is needed to develop the wave measuring system at navigation. In this report, we studied about the method of measurement of directional wave spectrum integrating several information on board including ship motion and RADAR image. Next, we extended Maximum Likelihood Method to following sea problem. For the verification of this theory and method, we carried out towing tank test and full scale ship test using same ship consistently. Finally, it was shown that this integrated method using ship motions and PPI image of the RADAR give fairly good results.