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Old 06-11-2019, 11:09 PM
brossa is offline
Join Date: Feb 2005
Posts: 1,141
Originally Posted by Chessic Sense View Post
Well yeah, I realize that, but do you think it would be enough curvature to matter? If you're not at extreme latitude and you're not near the solstices, it shouldn't be enough of an arc to make a difference in the overall escape plan, I wouldn't think. If you take measurements, say, 3 times at 2 hours apart, the arc is essentially removed, right?

Perhaps I'm wrong and the arc is more pronounced than I give it credit for. Still, we're only using it to orient ourselves, not to calculate any precise coordinates, so that I can convey the island's shape via the chess board description. What am I missing?
Take a look at The Photographer's Ephemeris and play around with the slider on the blue bar at the bottom of the screen. There's a tutorial video here that explains what you are seeing as you slide the time around. It shows a representation of how a shadow moves and changes length over the course of a day as a thick dark brown line: yes, the arc can be quite pronounced.

At my current location, for today's date, if I plotted the shadow near dawn and one hour later, the resulting line would run almost 45 degrees off the true E-W line. The shadow for today swept around 245 degrees, starting in the SW, swinging to the north, and then to the SE at sunset.