NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Dip uncertainty
From: Bruce Stark
Date: 2004 Dec 8, 16:48 EST
From: Bruce Stark
Date: 2004 Dec 8, 16:48 EST
George and Alex point out than, since my plate-of-glass-on-a-buoy picture doesn't allow for any nonstandard bending once light has passed the buoy, it isn't realistic. That's a problem all right.
George gives us a realistic model in which a ray of light skims past his ear (as he stands in the cockpit of his boat) and goes on to the eye of a navigator on the bridge of a ship. George says: "The anomalous part of the dip will be, initially, the same as affected me at 2.8 miles [from the horizon], but now the light goes on, still close (from 6 to 24 ft) to the sea surface, so there's extra curvature added as a result of that additional 2.8 miles of its path."
I won't argue that point either, not directly. But it could be misleading.
To deal with it I'll have to simplify because, in the real world situation George has set up, if you shift from "normal" to "abnormal" refraction, things get squirrely. Distance to the horizon changes. And, if the ray that skims past George's ear is still going to get to the eye of the man on the ship, heights of eye, and/or distance between George and the ship have to change.
Let's suppose, first, that light normally comes from the horizon in a strait line. Also, that when light is bent "abnormally" the distance to the horizon doesn't change.
George gives us a realistic model in which a ray of light skims past his ear (as he stands in the cockpit of his boat) and goes on to the eye of a navigator on the bridge of a ship. George says: "The anomalous part of the dip will be, initially, the same as affected me at 2.8 miles [from the horizon], but now the light goes on, still close (from 6 to 24 ft) to the sea surface, so there's extra curvature added as a result of that additional 2.8 miles of its path."
I won't argue that point either, not directly. But it could be misleading.
To deal with it I'll have to simplify because, in the real world situation George has set up, if you shift from "normal" to "abnormal" refraction, things get squirrely. Distance to the horizon changes. And, if the ray that skims past George's ear is still going to get to the eye of the man on the ship, heights of eye, and/or distance between George and the ship have to change.
Let's suppose, first, that light normally comes from the horizon in a strait line. Also, that when light is bent "abnormally" the distance to the horizon doesn't change.
