therion-doc 5.4.4ds1-5ubuntu2 (amd64 binary) in ubuntu groovy

 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.