User's Manual

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7
System Overview (Continued)
System Operation
In order to provide positional data to the vessel’s DP system, the Artemis system needs to
be “locked”. In this state, the antennae of the Fixed and Mobile Stations are facing each
other and automatically tracking by maintaining a continuous microwave link.
The distance between the sensors is obtained from the travel time of the microwave signal,
measured by means of coded interruptions in the continuous wave. The bearing of the
Fixed Station, with respect to the centre line of the vessel, is measured using a precision
shaft encoder.
The Fixed Station measures the Azimuth and reports it to the Mobile Station. The Azimuth
is the horizontal angle between a reference direction and the Mobile Station, with its vertex
at the Fixed Station.
Beacon Unit
Used instead of a standard rotating Fixed Station on a fixed platform for absolute
positioning, or on a moving platform or structure for relative positioning. The antenna
of a Beacon unit does not rotate, and three types of antenna are available for different
situations:
A. Omni directional antenna with 360° beam width
B. Semi-omni antenna with waveguide, 100° beam width
C. Horn antenna with 66° beam width
Layout of a Standard Artemis System
Different Types of Beacon Antenna
Layout of an Artemis Beacon System
The beam width of an antenna unit (Fixed or Mobile Station) is approximately 2°.