ISEP 2012 VTS IMPROVEMENTS – INTRODUCTION OF WAVE MONITORING SYSTEM AS A NAVIGATIONAL SENSOR Serdjo Kos, Renato Ivče, David Brčić University of Rijeka – Faculty of Maritime Studies Studentska 2, 51 000 Rijeka skos@pfri.hr rivce@pfri.hr brcic@pfri.hr Abstract The possibility of unwanted effects appears whenever the ship experiences significant wave forces, which reflects on ship’s surfaces, causing uncontrolled motion and behaviour. These effects may occur during navigation, port and coastal approaches or especially while the vessel is berthed alongside. If, due to high seas, mooring of the vessel fails, there appears a risk of ship’s damage, not to mention accidents due to sudden interruption of cargo operations. The paper elaborates the integration of ship’s navigational bridge with systems of wave force monitoring, with the aim to avoid mentioned consequences. Key Words Integrated Navigation Systems, Wave monitoring System, Wave forces 1 INTRODUCTION Radar has become both obligatory and inevitable navigational tool for collision avoidance, as well as for navigation in coastal waters. Radar’s emitted electromagnetic pulse bounces off the objects in the surrounding of the ship (more specifically radar’s antenna) and returns showing the presence of detected objects on a specific point. By knowing the position of desired object and calculating the further, the navigator has a competent insight in the dynamical situation which takes place. However, not all of the received signals are favourable. The signal which travels back through the antenna, the receiver and finally displayed on the radar screen, is composed both of useful information regarding ship targets, coast and/or other objects, and unwanted echoes with their origin in the state of sea and wind, precipitation, interferences and other numerous accidental or deliberate effects. In heavy rain, for example, the radar image will be masked with scatters representing rain drops all over the corresponding area in which the precipitation occurs. As for the nuisances regarding sea state, the result on the screen will be similar, indicating from which direction the waves are coming, and from where wind blows, respectively. Mentioned effects are nowadays effectively suppressed with various controls, and certainly with the skills of the navigator. One of the nuisances, the Sea Clutter, will be mentioned in the further text in a complete opposite context; the unwanted echoes from waves can be used to measure the actual state of the sea, which represents essential information regarding wave forces and their impact on the berthed or approaching ships. Acting as a sensor, this system provides accurate real-time information regarding wave forces and their load on the surface of the vessels. Beside ships, this information is also important to the Vessel Traffic System (VTS) and the Pilot Office, as well as to shore facilities, in order to prevent bursts of the mooring lines or the abruption of cargo operations due to excessive forces. The following text gives an insight to the importance of data regarding wave loads, and also elaborates the possibility of integration of such a system on the Integrated Bridge. In this way the vessel gives an insight of her surrounding to all concerned parties providing timely response. 2 WAVE LOADS AFFECTED ON BERTHED VESSEL Ports and terminals around the world have various berthing layouts and mooring facilities that are exposed to different wind, wave, tidal and swell conditions 1 . Ship's master must take into consideration the critical value of mentioned meteorological and oceanographic phenomena which are acting on berthed vessel in order to ensure that the vessel is adequately moored to withstand the anticipated forces. It is important that the ship's master promptly takes extra precautions to keep the vessel alongside in adverse weather and that is ready and able to vacate the berth safely when conditions make it difficult for mooring. Moorings are provided to prevent vessels from drifting away from a berth or from colliding with adjacent moored vessels. Movement should be restrained by means of an adequate number of mooring lines, which can be readily handled by the operating personnel, compatible with the meteorological and oceanographic conditions during the period the vessel is berthed. The mooring equipment is dependent on the ship size and type and its position at port, spacing and strength of the mooring lines. In case that forces which are acting on ship's mooring lines exceed its breaking load, the mooring system will be disabled. The consequences of these incidents range from personal injury, significant contact damage to the vessel including grounding damage, damage to adjacent vessels, shore/terminal structures, and pollution damage to the environment. Wave loads on a vessel can vary depending on the vessel’s response to waves of varying periods and heights. When the wave energy in the berthing area is sufficient to cause significant movement of moored ships, several 1 This is especially important at berths that are not situated in port basins or bays, but off the shore, where the moorings (jetty's) are extracted out of the coastline.