Very interesting thread.
In your post you often trust to the button: "estimate speed and course", but this mean is it an
estimation or an exact data ?
I answer you this question because I use this tool to determinate AOB:
http://mysite.verizon.net/ress1z18/id4.html . (somebody use it?) I had to print the wheels but it is rather fun to use. But I need to know the exact target course to use it and this is my problem. I usually use the "drawing method" to find it (I draw 2 points along the target course and draw a line. Then I use compass to find the target course where the line is crossing the compass wheel).
But I often find some differences beetween this method and the estimate course the button give me.
What are you thinking about that?