therion-doc - 5.5.7ds1-2 main

Therion is cave-survey drawing and modelling software. This package
includes the thbook which is the specification for the therion data
description language. This is not the easiest way to get started;
there is much more documentation in the Therion wiki:
https://therion.speleo.sk/wiki/doku.php with introductory guides, FAQs
and examples. Read those first to get an understanding of how it is
used.