Performance

Availability of Aids to Navigation

The method of measuring Aids to Navigation and the recognised availability standards are set for each category of Aid by the International Association of Aids to Navigation and Lighthouse Authorities (IALA). These are published in the IALA Aids to Navigation Guide (NAVGUIDE - Fourth Edition December 2001). The Northern Lighthouse Board is a member of IALA and operates to these standards.

IALA states that the absolute minimum level of operational availability for individual aids to navigation is 95%. If availability of an individual Aid falls below this level then consideration must be given to withdrawing the Aid to Navigation from service.

The availability of the actual Aid to Navigation (e.g. whether the light is flashing correctly or a buoy is on station) is over a 3 year continuous period. High levels of availability, which matches or exceeds Internationally recognised standards, ensures that the Board provides the service required by mariners in our hostile marine environment.

Each of the Traditional Aids to Navigation operated by the Northern Lighthouse Board are allocated a category as follows:

Category 1
An Aid to Navigation that is considered by the Northern Lighthouse Board to be of primary navigational significance. It includes the lighted aids to navigation and racons that are considered essential for marking landfalls and primary routes.
Availability Objective for Category 1 is 99.71%

Category 2
An Aid to Navigation that is considered by the Northern Lighthouse Board to be of navigational significance. It includes lighted aids to navigation and racons that mark secondary routes and those used to supplement the marking of primary routes.
Availability Objective for Category 2 is 99.87%

Category 3
An Aid to Navigation that is considered by the Northern Lighthouse Board to be of less navigational significance than Category 1 and 2.
Availability Objective for Category 3 is 99.94%

How is it Measured
Availability is measured by dividing total time (i.e. the sum of the total number of hours in a year multiplied by the number of Aids to Navigation in each category) into the difference between total time and the number of hours that the Aids were not available to the mariner. This calculation is then expressed as a percentage.

Click here to see the current performance of our Aids to Navigation

If you require details on the performance of a particular Aid to Navigation under our jurisdiction please write to the Information Officer, Northern Lighthouse Board, 84 George Street, Edinburgh EH2 3DA.

Click here for List of Lights