Understanding GMDSS: The Global Maritime Distress and Safety System PDF
Preview Understanding GMDSS: The Global Maritime Distress and Safety System
Understanding GMDSS The Global Maritime Distress and Safety System L. Tetl ey I. Eng., F.I.E.I.E. Principal Lecturer in Communications Engineering D. Calcutt M.Sc., C.Eng., M.I.E.E. Senior Lecturer in Electronic Engineering Springer Science+Business Media, LLC © 1994 L. Tetley and D. Calcutt Originally published by Edward Arnold in 1994. First published in Great Britain 1994 British Library Cataloguing in Publication Data Tetley, L. Understanding GMDSS: Global Maritime Distress and Safety System I. Title II. Calcutt, D. 623.88 ISBN 978-0-340-61042-8 ISBN 978-1-4899-6619-3 (eBook) DOI 10.1007/978-1-4899-6619-3 All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronically or mechanically, including photocopying, recording or any information storage or retrieval system, without either prior permission in writing from the publisher or a licence permitting restricted copying. In the United Kingdom such licences are issued by the Copyright Licensing Agency: 90 Tottenham Court Road, London WIP 9HE. Whilst the advice and information in this book is believed to be true and accurate at the date of going to press, neither the author nor the publisher can accept any legal responsibility or liability for any errors or omissions that may be made. Typeset in Great Britain by Computape (Pickering) Ltd. Preface History has shown that changes are often made as a consequence of events. In addition, engineering changes are made as a consequence of the escalating development of technology. Both of these criteria have lead to a massive change in the methojs by which distress alerting and communications are carried out on a global scale. The embryo of a new global communications system commenced operation in February 1992, and will continue to be developed during the transition period leading to February 1999 when the Global Maritime Distress and Safety System (GMDSS) becomes fully operational. The GMDSS is already extending the frontiers·of mobile radio communications tech nology by building a complex highly reliable radionet to encompass the world, and take global mobile communications forward into the new millenium. Not since the year 1912 and the tragic loss of the RMS Titanic has there been such a radical change in the field of maritime communications. Much has been written in retrospect about the unfortunate Titanic. A considerable amount of criticism has been levelled at the resultant rescue operation which, in fact, took place relatively effi ciently within the guidelines valid at that time. However you view the tragedy, that singular maritime disaster instigated a necessary process of change which continues today. Maritime safety procedures are reviewed at regular meetings of the Safety of Life at Sea Convention under the guidance of the International Maritime Organization. Clearly, a critical element within the safety package protecting all those who sail the oceans of the world is radio communications and its ability to alert other vessels and shore establishments of an impending disaster. Radio communications within the GMDSS are composed of numerous elements forming a highly efficient radionet enclosing the entire surface of the world. Both terrestrial and satellite methods of communications are interlocked in order to produce an extremely reliable scheme whereby relatively inexperienced operators can use modern equipment to alert rescue authorities in the event of a vessel being in distress. However, whilst the use of satellite communications enables a shipboard operator to alert a shore-based rescue co-ordination centre rapidly, it should be remembered that a ship in distress requires immediate assistance which, in most cases, will be provided by shipping in the immediate area. Even considering the spectacular advances in tech nology, the human element still exists, and it is likely that distressed seamen will still be rescued by fellow seamen. Gone are the days of the dedicated maritime radio officer who communicated by Morse code, often using a strange vocabulary. He/she has been replaced by the on-board operator whose secondary task it is to operate the radio communications equipment. Whilst mariners allocated the task of being shipboard radio operators are required to hold a Certificate of Competency, the skills-training period is very short compared with that of a dedicated radio officer, even compared with those who sailed on the ill-fated Titanic. However, the immense advances made in electronic equipment IV Preface technology and system design have ensured that radio communications terminals can be operated very efficiently by virtually anyone. This book has been written to provide the new radio operator and the electro-techni cal officer with all the knowledge required to understand fully the GMDSS and its related systems. There are three major sections in the book. Section one provides detailed information on the GMDSS itself. The complexity of the interlocking methods of communications, position fixing and distress work are carefully explained, along with specific equipment operational techniques. Section two looks at the massive impact of satellite communications and explains fully how, using satellites in general and the Inmarsat system in particular, distress alerting and communications via this medium have become relatively easy procedures. In addition, the operation of satellite Ship Earth Stations produced by major manufacturers is explained. The principles of terres trial radio communications are considered in Section three, culminating in a description of some of the modern radio equipment available and its place within the GMDSS radionet. Finally, a detailed glossary and abbreviation section is provided which includes all those curious phrases, acronyms and buzzwords to be found in GMDSS literature and technical manuals. This is a reference textbook which, when read in conjunction with technical manuals, will enable the reader to understand the technology employed in modern maritime communications systems. A large number of diagrams, photographs and illustrations have been included in order to make the text readily understandable. The companion volume Satellite Communications: Principles and Applications has been written for use by maritime electro-technical officers, communications engineers and engineering students who require to analyse satellite communications system technology at a much greater depth. L. Tetley D.Calcutt 1994 Acknowledgements A book of this complexity dedicated, as it is, to a brand new topic - the GMDSS - must inevitably owe much to the cooperation of various individuals, equipment manufac turers and organizations. To single out one or more organizations is perhaps invidious. However, our sincere thanks go to the parent and guardian of the GMDSS, the International Maritime Organization without whom the GMDSS would not be the excellent system that it is today In many cases we have had no personal contact with individuals but despite this they gave freely of their time when information was requested. We are extremely grateful for the assistance that the following companies and organizations gave during the writing of this book. We are particularly indebted to those organizations who permitted us to reproduce copyright material. Our sincere thanks go to the following: Asea Brown Boveri (ABB) and ABB NERA AS. BT Inmarsat Customer Services. COSPAS-SARSA T Secretariat. EB Communications (Great Britain) Ltd, supplier of ABB NERA GMDSS communi cations equipment. The INMARSAT Organization. The Inmarsat quarterly magazine Ocean Voice. The International Maritime Organization (IMO). Japan Radio Company Ltd (JRC). Raytheon Marine Sales and Service Company, supplier of JRC GMDSS communi cations equipment. The following figures are reproduced with the kind permission of the International Maritime Organization, London. Figure 1.2, page 5. Figure 1.5, page 12. Figure 1.11, page 21. Figure 1.18, page 30. Figure 1.21, page 33. Figure 1.26, page 39. Figure 1.28, page 41. Figure 1.29, page 42. The front cover picture depicting the GMDSS concept was derived from an original illustration produced by the IMO. Last, but by no means least, both authors would like to thank their wives who provided constant support through the long hours spent pounding the keypad of the word processor. In memory of Ray Cowhig Contents Preface iii Acknowledgements v SECTION ONE THE GLOBAL MARITIME DISTRESS AND SAFETY SYSTEM 1 The GMDSS radionet 3 1.1 Introduction 3 1.2 The GMDSS system 4 1.3 Digital selective calling (DSC) 10 1.4 The GMDSS space segment 13 1.5 Emergency beacons 27 1.6 Search and rescue 29 1.7 Shore-to-ship alerting 31 1.8 The NAV TEX service 35 2 Equipment maintenance requirements 49 3 GMDSS personnel qualifications 60 SECTION TWO GMDSS SATELLITE COMMUNICATIONS 4 Satellite orbital parameters and outline satellite communication principles 65 4.1 Introduction 65 4.2 Satellite link parameters 73 4.3 Link budgets 77 4.4 Multiple access 83 4.5 Modulation and demodulation for satellite services 96 4.6 Digital transmission 98 4.7 Digital modulation 99 4.8 Coding 105 4.9 Error correction 108 5 The Inmarsat organization 113 6 The Inmarsat-A system 134 7 The Inmarsat-B system 169 viii Contents 8 The Inmarsat-C system 178 9 The Inmarsat-M system 195 9.1 Introduction 195 9.2 Which Inmarsat system? 199 10 Satellite mobile frequency bands 201 11 The future 203 SECTION THREE TERRESTRIAL COMMUNICATIONS 12 Signal propagation and the radio spectrum 207 12.1 Introduction 207 12.2 Marine communications systems and their frequencies 207 12.3 Radiowave radiation 208 12.4 Radio frequency spectrum 212 12.5 Radiowave propagation 216 13 Antenna systems 226 13.1 Introduction 226 13.2 Specialist antennae 235 14 Radiocommunications systems 240 14.1 Introduction 240 14.2 Voice communications 240 14.3 Telex communications 249 14.4 Data over radio 255 14.5 Transceiver systems 255 14.6 The MF/HF transceiver 258 14.7 The VHF transceiver 272 15 The future 286 Glossary of terms and abbreviations 287 Appendices 293 1 Examination syllabus guidelines for the GMDSS GOC 293 2 The decibel (bB) 298 3 Producers of ship terminals 300 4 Satellite telephone country codes 302 5 Satellite telephone services 305 Index 307 Section One THE GLOBAL MARITIME DISTRESS AND SAFETY SYSTEM
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