How often have you heard someone discuss the direction a vessel is sailing and mention the words "heading" or "course"?
Heading
The direction in which a vessel's bow points at any given time. It is the angle between North and the bow of the boat.
Course Over Ground (COG)
Course Over Ground is the actual direction of progress of a vessel, between two points, concerning the earth's surface. The vessel’s "heading" may differ from the Course Over Ground (COG) due to the effects of wind, tide, and currents.
💡Course Over Ground (COG) is the actual direction of motion (the intended direction of travel). 💡While heading is the direction in which a vehicle/vessel points at any given moment. |
Voyage route through waypoint A, B, …, F.
The vessel starts by heading 90 degrees to the east.
A to B vessel is moving smoothly without failure so that the track can be defined as a straight line to the east direction.
Heading, and the COG value will remain the same.
The next step is point C.
The vessel has to deal with strong wind, current, and tide from the south side.
To keep the voyage on track, the heading changes to 135 degrees against the wind, current, and tide.
Until point D was reached.
COG will remains the same (90 degrees).
At point D, the storms have passed.
Back to travel with an ideal situation.
Waypoint E is 135 degrees from point D.
The heading was kept at 135 degrees.
Point E changed the heading as the final destination (point F) was 90 degrees to the east.
Point E to F is the same as the trip from point A to B.