NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Pike
Date: 2023 May 17, 03:13 -0700
Homer Smith
Re: your lake horizon question. The best thing to do is try it and see. You could compare your result with Frank's GPS Anti Spoof App. The dip tables certainly go that high. They used that technique on the R34 Airship Atlantic crossing in 1919. Their problem was not the dip tables but knowing their exact height when no updated surface pressure was available. They got round this by shooting the length of their shadow. You don't have that problem because you know your height above sea level. Your problem might be knowing the height of the water in the lake. However, the overall error could be small, because when you look at the dip tables you'll see the difference in dip for a small error in height reduces with the height above sea level of the observer. Incidentally, It depends upon where you live, but near me the days when you can actually see the horizon 34 miles away are relatively few. Altenatively, use an artificial horizon or buy a decent bubble sextant. The photo is from Norie's 1963. DaveP
