A critical look at the IMO requirements for GNSS J. O. Klepsvik, Kongsberg Seatex, Norway P. B. Ober, Integricom, Netherlands M. Baldauf, Hochschule Wismar, Germany BIOGRAPHY John O. Klepsvik is Principal Engineer for R&D at Kongsberg Seatex and project manager for Galileo maritime application projects. His area of specialisation includes radionavigation, sonar and laser radar. He is currently a member of RTCM SC 104 and IEC TC 80 and holds a MA and Dr. Ing in Applied Physics from the Norwegian University of Science and Technology (NTNU). Pieter Bastiaan Ober obtained his PhD from the Technical University of Delft in 2003. His areas of experience include the influence of multipath on GPS positioning, carrier phase differential GPS, ambiguity resolution and in particular integrity monitoring. He has undertaken a variety of studies in the use of navigation systems for different modes of transport, has performed performance analysis studies and has designed and developed positioning and integrity monitoring algorithms. Michael Baldauf obtained his Ph.D. in Safety Engineering and is presently employed as chief coordinator for research at the Hochschule Wismar, University of Technology, Business and Design. He went at sea as nautical officer on several cargo and container vessels after university. In 1993 he changed into the field of Scientifics and was employed at different universities and institutes. ABSTRACT The IMO Resolutions A. 915(22) and A. 953(23) form the backbone of IMO’s requirements for Maritime Radionavigation Systems. A.953(23) gives the formal requirements and procedures for accepting new systems as ‘components of the World-Wide Radionavigation System (WWRNS)’, while A.915(22) must be viewed as a ‘positioning’ document related to requirements for future developments of GNSS to be considered within the framework of A.953(23). However, none of the existing and planned GNSS seem to be able to comply with the IMO requirements, particularly the requirements for integrity and continuity, as reported in several recent studies. The paper examines the IMO requirements in view of the Galileo design requirements, notably the aviation (Level A) integrity and continuity requirements for the Safety of Life service. The Level A risk allocations have been translated to the maritime scene of operation using risk exposure times appropriate for critical maritime navigation elements. In order to arrive at a consistent set of requirements, two different approaches have been analysed: a top-down approach based on a Target Level of Safety (TLS) requirement and a bottom-up approach based on a translated set of Galileo allocations. Both approaches seem to indicate that a total risk exposure time of 15 min or less will be required as a normalising risk period in order to allow present and future GNSS to comply with IMO requirements. THE ROLE OF GNSS IN SHIP OPERATIONS The maritime sector is well advanced in exploiting the opportunities of GNSS. GPS, GLONASS, dGPS and combined GPS/GLONASS have gained wide acceptance as the preferred positioning systems for a majority of maritime applications. The world-wide availability, high accuracy and fast rate of position updates has further fuelled the development of a number of other safety related systems and equipment. Recognising the importance of GNSS for present and future maritime navigation, IMO has in the revised SOLAS Chapter V, Regulation 19 stated that: All ships irrespective of size shall have a receiver for a global navigation satellite system or a terrestrial radio- navigation system, or other means, suitable for use at all times throughout the intended voyage to establish and update the ship's position by automatic means. 1931 ION GNSS 20th International Technical Meeting of the Satellite Division, 25-28, September 2007, Fort Worth, TX