N O T I C E T
O M A R I N E R S
(No. 28 of 2006)
_________________
___________________
GLAs
PUBLIC DGPS TRANSMISSIONS
Northern Lighthouse Board
DGPS is provided as a
marine aid to navigation, giving all year round service with overlapping signal
coverage up to 50 nautical miles around the coasts of the
All mariners are advised:
1. DGPS relies inherently
on GPS, the operation and characteristics of which is under the control of the
US Department of Defense. Users are cautioned that the signal availability and
accuracy may be subject to change without warning.
2. The DGPS service is
provided primarily for use in monitoring the integrity of GPS to enhance the
safety of marine navigation. The provision of greater accuracy for marine
navigation is a secondary feature.
3. Signal reception may
become unreliable, under certain extreme environmental conditions, towards the
limits of the geographical coverage.
4. 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 DGPS users should use all alternative means available to cross check the
information received. Users should also ensure that they have a receiver, which
gives sufficient warning of the complete loss of the DGPS signal and reversion
to GPS.
5. Various DGPS receiver
types are available, some of which may not provide appropriate or timely
warnings in respect of the system.
6. Reference should also be made
to Volume 2 of the Admiralty List of Radio Signals. In particular, mariners’
attention is drawn to the section dealing with the horizontal datums on charts
and satellite- derived position notes.