WOP is the point on the initial course at which the wheel is put over to initiate the turning of the vessel.
The distance between the WOP and the point at which the ship commences its turn is denoted by „F‟ and depends on the size of the vessel, its loading condition, speed, trim and type of the vessel, etc. „F‟ distance is obtained from the manoeuvring characteristics of the vessel.
To calculate the WOP, we first decide the turning radius R and draw the curved track (arc AC). Now, we calculate the distance between WP (B) and the WOP using the formula:
F sin ϴ + R (1-cosϴ)
Where „ϴ‟ is the difference between the initial & final course.
What is wheel over line?
- If we have cross track error on the initial course, we can continue and commence alteration on reaching the wheel over line. It is a line parallel to the final course, which cuts the initial course at the WOP.
- The distance at which the Wheel over line is to be drawn parallel to the final course is given by the formula: Distance = F sin ϴ + R (1-cos ϴ) (Where „F‟ is the distance between WOP & point when the vessel begins to turn, „R‟ is the radius of the turn and „ϴ‟ is the difference between the initial & final course)
- The value of F can be obtained from the ship‟s manouevering characteristics.