Guidance and decision-support system for safe navigation of ships operating in close proximity.

Abstract

This thesis studies the control and operational aspects of Ship-to-Ship (STS) operations. The aim of this tool is to enhance the efficiency and safety of these operations. A stepwise approach has been selected. The first step includes specification, development and testing of the tool in a simulated work environment using full-mission simulators. In the second step the findings from application of the tool in the simulated work environment will be used to develop a prototype which will be tested during real life STS operations. This paper describes work done in the first of these two steps. In the coming years, STS operations are expected to significantly increase both in frequency and geographically. This may involve carrying out lightering operations close to coastlines that may be sensitive to environmental emissions. This thesis presents the operational challenge of the hydrodynamic interaction effects and an evaluation of the operational limitation based on a towing tank model test programme and on simulations of STS manoeuvre in lightering operations. The concept of ‘Danger Zones’ due to hydrodynamic interaction is introduced, which visualizes and tries to quantify the potential danger as a function of the vessels’ intra-ship positions. Using interviews and questionnaires, a survey was carried out among experienced mooring masters, the officers in charge of these operations. This identified a need to supplement the visual observation with more accurate real-time information, and thereby improve the decision-making process. Different sensor technologies for accurate measurement of relative motions between moving objects, is also presented. The decision-making process for navigation at sea in general, and for the mooring master involved in STS lightering operations in particular, has been reviewed. A model of the decision-making cycle, using contextual observations and interviews, has been proposed. During four iterations, a tailored-made Graphical User Interface (GUI) was made following Interaction Design (IxD) principles. The alternative designs were iteratively developed and tested by mooring masters and experienced ship’s officers in a shiphandling simulator. Semi-structured interviews were used, to show the mooring masters’ decision-making process and operational understanding. Key information was clarified to enhance their situation awareness (SA) and decision making process. This analysis led to the IxD development of a prototype guide and decision-support system (DSS). This is tailor made to aid the approach between two vessels whose objective is to position alongside each other while maintaining forward speed in open waters. An initial performance test using a realistic lightering operation was carried out in a ship-handling simulator. The purpose of the test was to identify improvement indicators in the performance using the prototype DSS. This test showed that a tailor made GUI on a DSS can improve the existing simulator based training activities in STS operations.