One of the first articles ever
written about using least squares to close cave survey loops
appeared in the NSS Bulletin in 1970. It was titled "The
Application of the Method of Least Squares to the Closing of
Multiply-Connected Loops in Cave or Geological Surveys,"
and was written by V.A. Schmidt and J.
The concepts presented in the article has been
used as the basis for loop closers for several different cave
survey programs. Since the article has been out of print for a
long time and it is virtually impossible to find anywhere on the
internet, I've scanned my copy and posted it here: