# NavList:

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

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Re: Coastal Plotting Sheets
From: Bill B
Date: 2007 Mar 28, 00:50 -0400

```> From: Michael Bradley

> To do the geometry, you draw a 'base line' between the
> two known objects, take 90 deg minus the observed
> angle = x, draw a line from each object at angle x to
> the base line. Where these two lines meet is the
> centre of the circle, which you can then draw with
> circle passes through the fixed objects.

I'm lost here.  If I draw a line segment between the two points, as I
perceive it the rest is about impossible.

Is it possible the "base line" is drawn at 90d to the line segment (chord)
connecting the two points, equidistant from the two points?

It occurs to me an alternative solution would be to use a course protractor
set to the angle to establish 3 or 4 points a good distance apart, connect
the points to form chords, bisect the chords and draw lines 90 from the
bisection point.  Those should pass through the center of the circle as
well--but more work and more chances for drafting error.

Thanks

Bill

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