This is Therion, cave surveying software. 

It produces complete, always up-to-date cave maps. The map is automatically 
updated after loop closure, blunder fix or map symbol set change. 
It's particularly well suitable for documenting large and complicated cave
systems.

Therion creates realistic 3D models from 2D maps without quantity of additional
information. LRUD dimensions are also supported.

Documentation is in the Therion Book (file thbook.pdf), which can either be 
downloaded from the internet or compiled in the `thbook' directory using pdfTeX.
Installation (compilation) is described in the Appendix of the Therion Book.

There is also much excellent documentation contributed by users on the wiki at:
https://therion.speleo.sk/wiki/doku.php

Web page: https://therion.speleo.sk

Copyright (c) 1999-2017 Stacho Mudrak, Martin Budaj

Distributed free under the GNU General Public License