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.