NavList:

Celestial and Visual Lines of Position with error.
There are many similarities between the two Lines of positions.
The Navigator may find his sextant error or his compass error by understanding the mechanics of each.
If the Navigator shoots back to back (reciprocal) sights North, South, East or west (or between)the double total error will show on the plot if horizon is not the error. The possible correct line and error amount is between the back to back. If the body’s azimuth is with-in 180 degrees of each other the Observer position is outside of the resulting triangle. It is always good practice to place an arrow in the azimuth direction for each body to analyze a sight.
The Navigator may find his compass error by taking opposite (reciprocal) bearings. The Line of Position will leave the observer between the two lines; if the Navaid are near equal distance the correct LOP will be in the center. If Navaids are greatly different than the distance ratio will indicate the distance between the plotted lines.
If the Navaid bearings are within 180 the Observer will be out-side of the resulting triangle.

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