Years and years ago I spent a few years learning all I could about the theory of surveying and survey adjustment.
I also looked at some of the code released for cave surveying, and was really offended at just how bad some of it was.
There were lots of little programs making no special claims about methods, many of which were interesting. There were some that had pretensions of fancy mathematics. Most of those were troubling to me.
I got into some of those programs and was even more offended by the lack of knowledge of the basics some programs showed.
At that time I campaigned (more or less unsuccessfully) to get cave survey folk to read real survey books and papers, and campaigned to the point of annoyance against cavers having their own specialized vocabulary separate from the survey community. [E.G. Cavers were using "string" for "traverse".]
I then got sidetracked for many years.
My real surveying stuff (that is not for the cave surveying audience) is at http://www.cc.utah.edu/~nahaj/survey/index.html
If you were pointed at my page, you probably came looking for one of the following articles.
Using Fore and Back sights to deal with Magnetic anomolies
This is a basic introduction to correcting for magnetic anomolies using foresights and backsights. It is a basic article, and doesn't address blunders.
Internal Angles Article
My Internal Angles Article shows how foresights and backsights can be used to compute internal angles, and use them to distinguish blunders from magnetic anomalies, and how to correct the blunders if there is redundancy.
The article also demonstrates why the "average foresights and backsights" practice of many cave surveyors (and cave survey programs) destroys valuable information.
I have prepared a minimal Bibliography for those that wish to read up on the subjects themselves.
I always try to get cave surveyors to read "real" survey publications. I've found that the ones that have are a lot easier for me to talk with.
Critical comments article
I published some critical comments on current practice of "least squares" cave survey programs.
This article gives specific objections to various current practices in the cave surveying field.
Skimpy start of an article introducing people to analysis and adjustment of surveys using Least Squares Methods. This article is not ready for publication by a long shot, but is visible to encourage early feedback as the article and support material is being written. Feel free to give me feedback at John.Halleck@utah.edu.
The point of the article is so that there will be a place cave surveyors can go to get an overview of the methods, and some sample (reference) code, and some standard test data.
There is a code library that is being written to match the introductory article.
As it is currently being built, all routines and interface are subject to change. It is being made available to encourage early feedback as the routines are being written.
There is now a discussion list being used by the reviewers of the
introduction article, and other interested parties. Requests to join can
be directed at
(The list is firstname.lastname@example.org)
Yes, I'm being outspoken on cave survey adjustment issues. This should not be confused with thinking this is really an important issue to me. Personally, I really don't think it matters much what sort of adjustments cave surveyors make on the data to produce a map. Almost anything is good enough for a map.
If you say you get your adjustments by reading tea leaves, you'll get no complaints from me if that's what your documentation says. If you get your adjustments from the methods you translated from a document written by the Roman Emperor Augustus, and your documentation says that, you'll also get no complaints from me.
If you get your adjustment from mathematical technique "Whatever", with some assumptions or simplifications, and those are documented (The WALLS cave survey program is a good example of one that documents the assumptions and simplifications) you'll also get no complaints from me.
HOWEVER, if you say "My adjustments are the mathematical technique XXX and are better than anything else.", then you can expect me to complain loud and long if it doesn't fully implement XXX and the documentation doesn't cover the differences. You can also expect me to complain if you don't seem to know the basics of method XXX.
Writing programs is always a trade off between what is "right" (almost a religious issue) and what is worth the implementation effort. Assumptions and simplifications are almost unavoidable. It is not assumptions and simplifications, per say, that I campaign against. It is UNDOCUMENTED assumptions and simplifications that I complain about, or cases where the author obviously doesn't understand the theory well enough to even understand that he (or she) is even making assumptions.
My personal option is that:
This page is http://www.cc.utah.edu/~nahaj/cave/survey/ © Copyright 2005 by John Halleck, All rights reserved. This page was last modified on Monday, July 11th, 2005