Sometimes if I am patrolling in a grid area I will not use the plotting tool but steer manually or set the course using the pop-out compass. (I use the most recent version of GWX). I have noticed that after about an hour I have a significant change in course. Last night I set a course on relative calm seas at 30° @ 8k. In one hour my course heading was @ 22°. Usually I use time and speed for calculated distance which pretty much works for me, however I was wondering about the drifting. Is there a ocean current influence in SHIII and if so is there usually a course correcting time-table if in manual steering? I didn't take heed about wind variations, so next time I'll need to pay attention and see if that is it also. But no wind and calm seas?
FYI: I do use the plotting tool for my longer trips to an area or going home, but I like using manual/course settings when in "search mode"...