Our error triangle was computed on the basis of spherical trigonometry because that is the how celestial navigation was developed on earth. Here is what we need to do to get the result to plot on a cylinder that SH3 plays on.
We need to measure the distance between the error triangle and the longitude of the assumed position. That distance is 73 km. At a scale of 1 arcminute = 2 km, that suggests our error triangle is 36.5 arcminutes East of the AP longitude.
We need to divide that number by the cosine of the latitude. The result is 56.8 arcminutes. East of the AP longitude. Then we convert back to km and get 114 km East of the AP longitude.
Or just look up the value in the chart. We need to multiply by 1.556. So our 73 km is really 114 km.
Just a little painful, but necessary to maintain accuracy, especially at higher latitudes.
