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## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Bowditch Table 15
From: Bill B
Date: 2005 Jan 26, 16:25 -0500

```Jim

In my 1995 version, it is article 2203, and actually gives the correct
formula for table 15 (two terms under the radical symbol)!  I do not think a
chunk of text is missing, as the Explanation of  Navigation Tables uses a
parallel format.

Bill
> I searched through the rest of Bowditch 2002 for more references to the
> Table 15 procedure, and found this odd paraphraph in Chapter 22, Article
> 2202:
>
> "Distance by vertical angle between the waterline and the top of an object
> is computed by solving the right triangle formed between the observer, the
> top of the object, and the waterline of the object by simple trigonometry.
> This assumes that the observer is at sea level, the Earth is flat between
> observer and object, there is no refraction, and the object and its
> waterline form a right angle. For most cases of practical significance,
> these assumptions produce no large errors.
> D = sqrt[(tan^2a/.0002419^2) + ((H-h)/0.7349)] - (tan a/.002419)
> where D is the distance in nautical miles, a is the corrected vertical
> angle, H is the height of the top of the object above sea level, and h is
> the observer's height of eye in feet. The constants (0.0002419 and 0.7349)
> account for refraction.".
>
> I don't see why the Table 15 equation is given in this paragraph.  Looks to
> me like a chunk of text is missing between the end of "...produce no large
> errors" and the equation, and that in fact the second half, which contains
> the equation, belongs to a missing title that should describe "Distance by
> Vertical Angle Measured Between Sea Horizon and Top of Object Beyond Sea
> Horizon".  Can someone check an older Bowditch?

```
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