Trondheimsleia (tidal current fields in electronic navigational chart systems)
In cooperation between University of Oslo, C-MAP and the Norwegian Hydrographic Service a system for displaying tidal current in Electronic Chart Display and Information System (ECDIS) has been developed. Official Electronic Navigational Chart (ENC) in compliance with the International Hydrographic Organization (IHO) S 57 Standard has been used in the implementation.
The tidal current fields can be displayed in real time on the electronic navigational chart and several options and functions for updating and zooming have been designed. The current fields are calculated from a data base with the harmonic constants for the four major tidal constituents. The harmonic constants are obtained from a high resolution numerical model which is validated by comparing with sea level and current measurements. The depth matrix for the central part of the model domain was calculated from data from multi-beam bathymetric surveys. An application example of the implementation is given for Trondheimsleia, a part of the main sailing route along the western coast of Norway.
Note: Only tidal current is calculated in this project
The figures belows are from two selected areas; The Garten-Storfosna channel west of Ørlandet, and Agdenes at the mouth of the Trondheimsfjord. The examples are from a period with strong tidal currents in late February 2002 due to coincidence of full Moon and lunar perigee on 27 February.
Screen 1 - The screen display of the electronic navigational chart for a section of Trondheimsleia southwest of Ørlandet at the time of the peak out-going (ebb) tidal current. 28 February 2002, 14:00 UT.
Screen 2 - The screen display of the electronic navigational chart for a section of Trondheimsleia southwest of Ørlandet at the time of the peak in-going (flood) tidal current. 28 February 2002, 20:00 UT.
The tidal current dominates the current variability in the area around The Lofoten Islands. The University of Oslo (Moe, Ommundsen and Gjevik, 2002) has earlier developed a numerical model with grid resolution 500 m for the area, but for a detailed study of the tide in the narrow sounds, e.g. Tjeldsundet and Ramsundet, finer resolution is required. In cooperation between the Norwegian Defence Research Establishment (FFI), University of Oslo (UiO) and the Norwegian Hydrographic Service (NHS) a depth-integrated numerical model with grid resolution 50 m will be used to simulate tides for Tjeldsundet and surrounding areas
For Tjeldsundet and Ramsundet a finer grid resolution of 25 m will be used. The depth matrix used for the simulations are for a larger part of the area based on modern multibeam bathymetric surveying. For validation of the model, sea level measurements at 5 locations were made in the period 31 January – 4 March 2004. Current meters were deployed in November 2004 and will be recovered in March 2005.
The figures below show the north-going and south-going tidal current in Tjeldsundet from the model with grid resolution 500 m.
Further work on tidal models
The project in Trondheimsleia and Tjeldsundet are pilot projects as a part of a larger plan on developing high resolution tidal models for areas with strong tidal currents along the Norwegian coast. The tidal currents can then be implemented in an electronic chart system. Tidal currents together with other Marine Information Objects (MIOs) in an electronic chart system can be useful information for navigation and marine operations in narrow coastal waters