Tidal overlay and dynamic ECDIS-a giant step from paper chart and tide tables

The Electronic Navigational Chart (ENC) is likely to replace the paper chart in the near future, at least for the SOLAS class vessels, and the Electronic Chart Display and Information System (ECDIS) is about to become commercial reality. At this stage, it cannot yet fulfil its promise of showing dynamically all the Time Varying Objects (TVO) as the IMO/IHO requirements specifically forbid dynamic representation of tidal heights. However, the first step towards changing this situation has been made with the preparation of tidal overlays for ECDIS by some forward looking ECDIS manufacturers. The tidal overlay for ECDIS has multiple advantages over its predecessor-the printed tide tables. In addition to the provision of the official tidal predictions it can model tidal heights for any given time and place rather than just the extremes of height at the standard ports. The same applies to tidal streams or currents at the critical locations. The system will be also capable of interfacing with the real or near-real time data provided by short-term forecasts, shore transmitters or satellites. Dynamic representation of flows, both tidal and non-tidal is expected to precede that of tidal heights, as there is no IMO/IHO restriction on this information. It is expected that the regulation forbidding dynamic representation of tidal heights will be removed as the users voice their requirements. Incorporation of other TVO into ECDIS is also discussed. The latest developments in the field of TVO seem to promise an easy transition to a fully dynamic, four-dimensional ECDIS of the future. Several problems however, both technical and organisational, will have to be solved before this goal can be achieved. On one side there will be a need for providing interfaces with real-time or near real-time information sources, short term forecast models and other data providers, and for developing the necessary standards. On the other, the relevant hydrographic offices (HOs) will have to determine the extent of tidal data applications, current and tide area encoding limits, methodology of supplying TVO data, etc. In some instances, where the HOs cannot provide these services, a Regional ENC Coordinating Centre (RENC) or commercial organisations may be required to help out.