NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Distance off with Chicago buildings
From: Bill B
Date: 2005 Oct 6, 22:43 -0500
From: Bill B
Date: 2005 Oct 6, 22:43 -0500
> So instead of using > the altitudes directly, use their difference: 8.7 minutes of arc. Ah, now I see. Very clever. If of you are 24 sm from the Hancock, and on the beach, you are either in Gary Indiana, or Highland Park, IL. The Michigan City cooling tower would not be visible from Highland park, so it must be Gary, nominally N 41d 37.7', W 87d 20.0'. Given a horizon 4-5 miles away, height of eye would be approx. 14 feet. It looks like you're walking the beach in Gary Indiana. At a steel mill perhaps? Interesting choice for a beach stroll.This is where I become deeply confused. Where does the 10.7' figure for the 361' cooling tower come from? The above location is approx. 23 sm from the Michigan City cooling tower. (Reference NOAA Chart 14905.) Therefore the land base and shore would be below your horizon at 14 ft height of eye. If I use Bowditch table 15, "vertical angle between top of object and sea horizon," you would be nominally 13 nm/15 sm away from the cooling tower with an angle of 11'. Not enough. If use plane trig with the assumption one could see the base/waterline, it works out within a < 1 mile. I have not checked out the separation angle yet, as I am very iffy about my building lat/lon (derived from Street Atlas). What have I missed? Bill