You could search the forums. I know there was a discussion some time ago about this effect and what causes it. I think that even though people who live in the northern hemisphere "know" shadows should be to the north, it is rare for people to see the real world from such an aerial vantage point. The inclination is to picture it mentally as a "model world" hanging on the wall in front of you, rather than you looking down on a horizontal surface. In this vertical orientation, lighting would typically be from above, or "up" on a map :0

-Rob A>