As per my previous posts, I did order the Garmin 4208 chartplotter and High Def radar. As many had said that I would need a flux gate compass to do overlay, I called Garmin yesterday to see what units would work well. Much to my surprise, their tech told me that I would not need a compass to do overlay as long as I was moving at 2 Knots or more. At lower speeds it would not work well, and I would nee the compass to use the MARPA abilities, but for basic overlay, the unit could do the computations itself.