If you are using the average COG to see in which direction the boat has sailed, you can end up with results that look different than expected.
Let’s say that the boat sails straight to the north (COG 0) for a minute with a speed of only one knot. Then it sails COG of 90 for another minute but with 10kts of speed. If we calculate the average COG, it will be 45. However, since the boat was going much faster toward 90 degrees, the actual course sailed was approximately 85 degrees.
This is the reason that to compare the courses sailed by boats, in the “Data” screen, you should use the “Course” value that shows the bearing from the first to the last selected point.