You have seen how the single proportion calculations are computed. However, there is another element you need to be aware of and that is Curvature of the Earth. The law requires all surveys of the Rectangular Survey System to be on the True Meridian. This requirement brings into play the concept that cadastral surveys in this true meridian system are on the surface of a sphere. This means that if you run a survey line due east or west, you must account for the curvature of the earth's surface. The Manual has a good discussion on the topic in chapter 2 and it is recommended that you study this chapter carefully. The following exercise will demonstrate how earth curvature can affect your final corner position in a single proportion calculation.

You have now completed the content for Unit 1. However, before moving on, complete the Unit 1 Section 2 Review Exercise on the following page.