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Safety, cost-effectiveness and environmental care are the most important aspects ship's route selection. Today, this latter aspect is gaining in importance due to the intense pressure from the community on those with the potential to reduce environmental pollution by reducing greenhouse gases (GHG) emissions. Maritime transport is certainly one of the significant contributors to global pollution and seeks to control and reduce it through conventions. One of the major factors in maritime traffic is the weather, but the assessment of weather conditions is not uniquely determined, which directly affect the motions and loads of the ship in the rough sea. This paper presents a six-year survey (2010-2016) and a comprehensive measurement campaign on a bulk carrier of the 28000 DWT class. The ship, known as the "tramper", had no fixed route, for a six-year period it sailed frequently in the South hemisphere. During the whole period, the navigational parameters such as weather data (wind speed and wind direction), wave data (wave height and directional wave spectrum), engine data (engine revolutions, engine power, fuel oil consumption, and exhaust gas temperatures on all six cylinders of the main engine), voyage data (ship speed, ship position, ship course), and motion data (pitch, roll, and yaw) were measured. Although mechanical troubles have occurred in 2-3 years of the measurement period, the ship has encountered many rough sea conditions as shown here. This paper compares the subsequently reconstructed weather conditions for several specific situations in which a ship operated. Using the meteorological and wave models, the Weather Research and Forecasting Model (WRF) and WAVEWATCH III (WW3), numerical simulations of the weather and sea state were conducted for eight rough sea cases using the grid point value (GPV) datasets National Centers for the Environmental Prediction Final (NCEP-FNL) and and the European Center for Medium-range Weather Forecasts Interim Reanalysis (ERA-Interim). Those simulations were validated using on-board observations of vessel performance and operation in rough sea conditions.

High winds, ocean current as well as wind-induced ocean waves can affect ship safety and navigation cost. To avoid such rough ocean states and make use of beneficial ocean current, an exact ship position considering about the weather and ocean information is of great importance. In our study, a powerful typhoon in the Kuroshio Current area of the East China Sea was studied to construct the Numerical Navigation System. Information of ocean winds, wind-induced ocean waves as well as the strong western boundary Kuroshio Current is firstly generated by modern weather and ocean models as a combination and then provided to a ship maneuvering model to construct a numerical ship navigation system. Effects of typhoon, wind-induced ocean waves as well as ocean currents on ship navigation could be found quantitatively by utilizing this method.

Various operations at sea, such as maintaining a constant ship position and direction, require a complex control system. Under such conditions, the ship needs an efficient positioning technique. Dynamic positioning (DP) systems provide such an application with a combination of the actuators mechanism, analyses of crucial ship variables, and environmental conditions. The natural forces of induced nonlinear waves acting on a ship&rsquo, s hull interfere with the systems. To generate control signals for actuators accurately, sensor measurements should be filtered and processed. Furthermore, for safe and green routing, the forces and moments acting on the ship&rsquo, s hull should be taken into account in terms of their prediction. Thus, the design of such systems takes into account the problem of obtaining data about the directional wave spectra (DWS). Sensor systems individually cannot provide high accuracy and reliability, so their measurements need to be combined and complemented. Techniques based on the recursive Kalman filter (KF) are used for this purpose. When some measurements are unavailable, the estimation procedure should predict them and, based on the comparison of theoretical and measured states, reduce the error variance of the analyzed signals. Different approaches for improving estimation algorithms have evolved over the years with the indication of improvement. This paper gives an overview of the state-of-the-art estimation and filtering techniques for providing optimum estimation states in DP systems.

A correct assessment of the ship speed loss in conditions of exploitation is becoming increasingly important for ship owners as well as ship designers. We are witnessing the increasing concern for the environment and awareness of the necessity to preserve it as much as we could. The ship speed drop in the real environmental conditions can cause the increased fuel consumption as well as increased emissions of CO2 and other GHG (greenhouse gases) from ships. Decrease of the ship speed in real conditions is a consequence of the added resistance due to the impact of weather conditions, i.e. waves and wind, and due to aggravated working conditions of propeller, i.e. engine system. Moreover, the solution estimation of this problem is very affected by human factors. Ship master, concerning for safety, can make a judgment that, under certain adverse weather loads, it is necessary to slow down or change ship's course to moderate or bypass the worst condition. In addition, the loading condition of the ship is constantly changing which govern the basic parameters of the ship: the mass and mass moment of inertia, draft and trim and, consequently, the ship behavior at sea. All these parameters affect the assessment of ship speed and it is necessary to be conscious of the intensity of their impact on the final value. At the same time, they cannot be predicted with absolute certainty so the purpose of this analysis is to estimate the impact of weather and operational uncertainties on the actual speed of the ship in real operating conditions.

This study evaluates the difference in speed loss, engine power, and fuel oil consumption of a bulk carrier from the viewpoint of weather routing. The evaluation of speed loss is important as speed loss influences accurate ship operation. The evaluation of speed loss is based on seakeeping and machinery theories. Speed loss due to added resistance is evaluated by different simulation methods, and the results are compared. Furthermore, to reproduce actual operations, three types of engine controls are considered. Numerical simulations for evaluating speed loss are carried out for a 20,000DWT-class bulk carrier in irregular wave patterns. No significant difference is observed in speed losses evaluated using the enhanced unified theory and new strip method when the mean wave period is longer. However, NSM underestimates speed loss if the mean wave period is relatively shorter. In addition, it is known that asymptotic formulae contribute accurate evaluations in a short period of waves. It is possible to implicitly evaluate speed loss under actual situations if these seakeeping models are combined with propulsion and engine control models. This study conducts basic research on this possibility to improve safe and efficient operation of vessels in rough seas. © 2017 Kobe University. This is the authors’ accepted and refereed manuscript to the article.