NavList:

Frank, Great explanation, but the quote below got me. Can I assume that you are talking about lunar distances that haven't been cleared for parallax? I thought all points on earth for a given instant of GMT would observe the same lunar distance once the parallax correction has been made. If this is the case then a "lunar distance line of position" would be a line of constant lunar parallax? -GeorgeB

From: FrankReed---com
Date: 11 Feb 2011 21:34

Like an altitude sight, every lunar distance makes a line of position for a given instant of GMT, as I've detailed on NavList and other places a number of times. This is not a standard celestial LOP. It's a different beast, and it was apparently quite unknown back in the heyday of lunars. The concept is simple enough: at a given instant of GMT, navigators anywhere along this line of position would measure the same value for the lunar distance. We can even use pairs of lunar distance LOPs to get a position fix without using any horizon at all. The existence of a "lunar distance line of position" means we can do the same trick as above and simply vary the GMT until the lunar distance LOP intersects the fix from the other sights.
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