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COG vs. Heading

gadangit

Member III
For the sake of this question we are assuming the water isn't moving.

Is it safe to assume that the amount of leeway a sailboat makes is the difference between it's heading and it's course over ground?

Chris
 

Charlie B.

Member II
COG VS Heading

Heading is the compass direction the boat is on, COG (measured by gps) is the track the boat makes across the bottom. The difference can be called leeway or drift assuming there is no current involved.

Charlie
 

ddoles

Member III
If you wish to be a bit more precise there is one additional factor involved, compass deviation. If you are determining your heading by reading from your compass it is not actually giving you the magnetic heading, but the compass heading. The difference between compass heading and magnetic heading is deviation. The amount of deviation will vary depending on the heading and can be determined by the painstaking process of swinging the compass. If you accurately know the deviation at your compass heading you can calculate the magnetic heading which you can then compare to the observed GPS COG, the difference being leeway.
 
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