Satellite navigation information services

During the development of the Global Positioning System there has always been a need to inform the users of GPS about the status of the constellation of satellites and the evolving policies regarding the operation and management of the system. As a result, various information services have been developed around the world, ranging from telephone recorded messages to computer bulletin boards. However, over the last years a number of factors have caused the future of these services to be reviewed. Firstly, GPS has now been declared fully operational, and therefore one could argue that there is now no longer a need for the same level, and immediacy, of information. Secondly, with the advent of global communications networks, such as the Internet, access to remote sites around the world is now easier and cheaper. Conversely, though one could also argue that there is an even greater need for reliable and timely information, with the increasing number of users of GPS and GLONASS, with the developments of the Inmarsat payload and the WAAS and EGNOS augmentations. This paper reviews the currently available sources of information on satellite navigation systems and the various means of accessing this information. It also presents and discusses the difficult issues of funding for these services and the liability of the service provider. It concludes with a speculative look to the future of information services.