The true azimuth (Zn) and the altitude intercept (a-int) are used to plot a line of position (LOP) on the chart.The line of position (LOP) is perpendicular to the true azimuth line, and is place on the chart at a distance from the assumed position (AP) equal to the altitude intercept (a-int).
The true position of the observer is located at the intersection of two or more LOPs. In this example, the LOP derived from the moon sight is in green, and from the Spica sight in blue.
If the recommended three LOPs are plotted, normally a very small triangle is formed near the intersection of two of the LOPs. In that case, the true position of the observer is located at the center of the small triangle.