Glossary
20221032B 177
10 GLOSSARY
Apparent wind – see relative wind
Arrival alarm – An alarm signal issued by a voyage-tracking
unit that indicates arrival at or at a predetermined distance from
a waypoint. (see arrival circle).
Arrival circle – An artificial boundary placed around the
destination waypoint of the present navigation leg, the entering
of which will signal an arrival alarm.
Arrival perpendicular – Crossing of the line which is
perpendicular to the course line and which passes through the
destination waypoint.
Bearing – The horizontal direction of one terrestrial point from
another, expressed as the angular distance from a reference
direction, usually measured from 000° at the reference direction
clockwise through 359°.
BPW – Bearing position to waypoint – Bearing to a specified
waypoint from present position.
BWW – Bearing waypoint to waypoint - Bearing angle of the
line between the “TO” and the “FROM” waypoint, calculated at
the “FROM” waypoint for any two arbitrary waypoints.
COG - Course Over Ground - The actual direction of progress
of a vessel with respect to the surface of the earth. The vessels
heading may differ from the course over ground due to the
effects of wind, tide, currents.
ECS – Electronic Chart System
For advanced navigation steering with preset radius in routes of
waypoints.
ECDIS – Electronic Chart Display Information System.
Type approved ECS system according to the ECDIS regulations.
GPS - Global Positioning System - This system consists of 18
satellites plus 3 spares in fixed orbits, circling the earth at an
altitude of approximately 20,200 km. The system will provide
the user with 24 hour a day all weather position coverage, with
an accuracy of 15 to 100 meters.
Great circle route – A course that is the shortest distance
between two points, following a great circle
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