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?