Now we close the error triangle with Gienah. Construct a bearing to Gienah from AP. Advance along this bearing 108 km because our Ho was 54' greater than the Hc. Construct a right angle Line of Position for Gienah. All points on this line are 108 km closer to Gienah than is AP. If we have done everything right, we are also on the Gienah LOP.
The Gienah LOP closes the error triangle. The size of the triangle gives us an estimate of the error of our methods. The triangle is very small. 3 independent measurements of star altitudes in game have yielded the same position to within about 2 km. It might not be the correct position yet, but it is remarkably consistent.
This error triangle was produced using almanac values calculated with spherical trigonometry. Our best measurement of our position says we are in that error triangle. And we would be pretty close if we had charted the result on a sphere.
So we need to correct the position of this error triangle to determine where it would chart on a cylinder. Like our navigation chart.
