In the last lesson, Unit 4, we dealt with problems in broken boundaries which included resurvey of nonriparian meanders. In essence, these methods again distribute the closing error in latitudes and departures proportionally along the length of each course. This is exactly like a common surveying rule, the Compass Rule Adjustment.

This rule assumes two things, that any errors are accidental and the effects of angular errors equal the effects of chaining errors. This is the essence of proportional measurement, equal distribution of any error along the entire line.

Grant boundary adjustments, in Section 2, of Unit 4 is similar in concept. With grant boundaries, you can think of the problem as a kind of photographic enlargement or reduction. The overall shape of the line should remain the same regardless of the amount of error at the end of the retracement. This shape conformity means that all anterior interior angles must what?