Notices to Mariners
Trial Loran-C Transmissions - Blink Pattern
12 - 2005
Issue Date: Friday 15 July 2005
The Commissioners of Irish Lights hereby give notice that the 'blink' pattern associated with the initial trial in the trial transmissions of Loran C is now removed. The trial transmissions will continue to be made in the frequency band 90-110 kHz from a location in Rugby in position Latitude 52° 22'. 009N, Longitude 01°11'.294W.
The signals are pulsed, with a Group Repetition Interval of 6731 (67,310 micro seconds) and an Emission Delay of 27,300 microseconds.
Mariners are reminded that:
- The use of LORAN-C as a navigational input is strongly encouraged to back-up the widespread use of GPS. Existing LORAN-C receiver users will require software upgrades from their equipment suppliers in order to use the new signal.
- Older receivers may have this station identity (6731-Y) listed as Loop Head and may produce significantly erroneous position outputs as a result. Owners of such receivers are advised to:-
- Manually exclude the use of this station if they can.
- Use the Time Differences directly, rather than relying on the receivers position solution, or
- Verify that the station has been automatically excluded from the position solution, or
- Update the GRI 6731 data manually if possible, or
- Contact their equipment suppliers for advice.
- The Loran-C transmissions are referenced to the World Geodetic System 1984 (WGS84) datum. Loran-C derived positions may be plotted direct onto charts referred to WGS84 datum. Most Loran-C and other integrated electronic position fixing receivers will have the facility to transform positions from WGS84 datum to the regional datum of the chart. However, the resulting accuracy will depend on the transformation parameters contained within the software of the users receiver. It is advisable therefore to keep the receiver referenced to WGS84 datum and to apply the position shift values denoted on the appropriate nautical chart before plotting a position. Position shifts for those charts, which do not include a "satellite derived positions" note, are listed in the UK Hydrographic Office annual summary of Admiralty Notices to Mariners Annual Notice 19.
- Signal reception may become unreliable, under certain extreme environmental conditions, towards the limits of the geographical coverage. The usability and accuracy levels of LORAN-C are highly dependant on the user's position within the coverage area; further details may be found in the Admiralty List of Radio Signals Volume 2.
- All radio navigation systems are susceptible to interference (including jamming) and environmental effects, which can adversely affect their availability. The GLAs strongly advise that no single aid to navigation system should be used in isolation and that users should use all alternative means available to cross check the information received.
- No responsibility can be accepted for the consequence of inaccurate positions obtained by means of these trial Loran C transmissions.
Notices to Mariners Nos 8 and 9 of 2005 also refer.
By Order, S. G. R. Ruttle, Chief Executive.