Notices to Mariners

Establishment of Trial DGPS Service

04 - 1998

Issue Date: Friday 15 May 1998

Aid:

Area:

The General Lighthouse Authorities of the United Kingdom and the Republic of Ireland - The Commissioners of Irish Lights, Trinity House and the Northern Lighthouse Board, will be providing an unencrypted Differential Global Positioning System (DGPS) service.
The DGPS service is being provided for use in monitoring the integrity of GPS and to enable greater accuracy for marine navigation.
Continuous DGPS transmissions on a trial basis will be progressively introduced by the Commissioners of Irish Lights from the following stations between 8th and 30th June 1998 approximately.

1. MIZEN HEAD LIGHTHOUSE
Latitude	51° 27' .05 N
Longitude	09° 48' .80 W
Identification Numbers
Reference Stations	660, 661
Transmitting Station	430
Nominal Range	100 miles
Integrity monitoring	Yes
Transmitted Message Types	3 5 7 9 16
Frequency	300.50 kHz
Bit Rate	100 bits per second
2. LOOPHEAD LIGHTHOUSE
Latitude	52° 33' .65 N
Longitude	09° 55' .90 W
Identification Numbers
Reference Stations	665, 666
Transmitting Station	432
Nominal Range	100 miles
Integrity monitoring	Yes
Transmitted Message Types	3 5 7 9 16
Frequency	312.00 kHz
Bit Rate	100 bits per second
3. TORY ISLAND LIGHTHOUSE
Latitude	55° 16' .35 N
Longitude	08° 14' .92 W
Identification Numbers
Reference Stations	670, 671
Transmitting Station	435
Nominal Range	150 miles
Integrity monitoring	Yes
Transmitted Message Types	3 5 7 9 16
Frequency	313.50 kHz
Bit Rate	100 bits per second

Mariners are advised that test transmissions may take place from the stations prior to the introduction of the trial service. Consequent upon the introduction of the service there maybe occasions when the service is switched ON/OFF for periods of up to 24 hours. The RDF Service from these stations may also be interrupted during these periods.
On all such occasions, advance warning of interruptions will be given to the relevant Coast Radio Stations and the Hydrographic Office.
Details of the DGPS station transmissions to be progressively introduced by the Northern Lighthouse Board and Trinity House will be given in Notices to Mariners to be issued by those authorities.
Mariners are advised that DGPS is referenced to the World Geodetic System 1984 (WGS 84) Datum. DGPS derived positions may be plotted directly onto charts referred to WGS 84 Datum. However the majority of charts for waters in which the GLAs have responsibility are not referred to WGS 84 Datum.
Most DGPS receivers will have the facility to transform positions from WGS 84 Datum to local chart datum. However, accuracy will depend on the parameters contained within the user's receiver.
It is advisable therefore to keep the DGPS receiver referenced to WGS 84 and to apply the position shift values denoted on the appropriate nautical chart before plotting a position.
Further informationis contained in the UK Hydrographic Office Annual Notices to Mariners 1998 and the Admiralty List of Radio Signals Volume 8.
Further Notices to Mariners may be issued as required.

By Order, T. M. Boyd, Chief Executive.