Now that you have completed the section on single point control. Let's extend the concept a bit further and apply all we've learned to another field problem. Our objectives in this section are to understand the concepts of irregular exterior adjustments and apply those concepts in known resurvey techniques to a problem with an irregular boundary line.

An irregular exterior adjustment is a method of distributing the distance between the record courses and the retracement courses for purposes of restoring intermediate corners which are lost on an irregular section or township line. It is a combination of two types of proportioning, one, done in the direction of the line, and the other done perpendicular to the line. Generally speaking, an irregular boundary is one which has a deflection in alignment.

The following examples demonstrate how these irregular exteriors can occur.

First, some township lines were surveyed in segments at different times and from opposite directions. When a connecting survey was made, it showed a deflection in alignment for that portion of the exterior.