therion and xtherion rely on environment variables and initialization files to configure their execution behaviour.

therion uses the following environments

• THERION, search path for the initialization files;
• HOME, the path $HOME/.therion is used in the search of the initialization files when these are not found in the path THERION (or the latter is not defined);
• TEMP and TMP are used to make the path of the directory for the temporary files. These are $TMP/th$PID, where $PID is the process id. They are also used for the path of the debug directory whree the temporary data files are saved, $TMP/thDEBUG.

The inizialization files, "therion.ini" and "xtherion.ini", respectively, are text files written with a syntax similar to the data files, ie, with command lines and comments (these start with the character '#').

Therion searches the initialization files in the following directories (on Linux; on Windows after the first two things are a little different), in the order:

1. $THERION
2. $HOME/.therion
3. /etc
4. /usr/etc
5. /usr/local/etc (this is the default installation place)

The search stops when an initialization file is found. If the initialization file is not found therion uses the default values (hardcoded in the program). The commands of the initialization file are:

• "encoding-default", defines the default output encoding;
• "encoding-sql", defines the encoding for the data exported in the SQL scripts;
• "language", defines the language for the output legends. For example "language fr";
• "loop-closure", defines the loop closure algorithm. It can be either "survex" (default) or "therion" (a simpler algorithm);
• "mpost-path", specifies the path of MetaPost. The default is "mpost";
• "pdftex-path", specifies the path of pdfTeX. The default is "pdfetex";
• "source-path", is the path of search of the input files (.th e .th2) and the configuration file ("thconfig").
• "tmp-path", specifies the directory where the temporary directories should be created. The default is "/tmp".
• "tmp-remove", defines the command to remove temporary files.
• "tex-env" used only in Windows (TODO);
• "tex-font" specifies the fonts for an encoding. It ha syntax "tex-font encoding rm it bf ss ssi", where the name of the encoding is followed by the fonts for the five styles: normal, italics, boldface, sans-serif, and sans-serif italics.

The initialization file of xtherion contains a list of variables that modify the behaviour of the program. The values of these variables can be set by replacing the default one. Among the others we have

• the work directory. This is the directory where xtherion starts from, when it opens the files. I found it convenient to set it to the subdirectory "Caves" of my home directory, because i keep there all the surveys: set xth(gui,initdir) $env(HOME)/Caves.
• the language used in the interface of xtherion. You can set it uncommenting the line ::msgcat::mclocale XX. Replace "XX" with the code for your language. It must be one of the languages compiled into the program, otherwise xtherion uses english.
• the fonts, either for the editor window or the interface labels. To specify the fonst uncomment the lines set xth(gui,lfont), for the labels, and set xth(gui,efont), for the editor. For exmaple (you can get the font names with xfontsel),
  set xth(gui.lfont) {-adobe-bookman-light-i-normal--0-0-0-0-p-0--- }
  Another way to set the fonts and other properties of the interface of xtherion is through the tt{Xresources} file. For example

    xtherion*background: #A0B0BF
    xtherion*font:     --lucida-medium-r-normal-sans-14-140------
    

To set the keyboard encoding to suit your keyboard change the value on the line with set xth(app,sencoding) to your codepage. To get your codepage in the Window->KBD Encoding menu item add to the xtherion initialization file the line lappend xth(kbencodings) codepage (with the proper name of your codepage, eg, cp1252).

Therion relies on three external programs to compile the maps of a project:

• cavern, to process the survey data;
• metapost, to process the scraps;
• pdfTeX, to put together the scraps and form the maps.

Indeed you can see in the output of the project builds (the lower part of the compiiler window in xtherion) the outputs from these programs.

xtherion writes the input files, both data files ".th" and ".th2" and configuration files, on disk, so that they are in sync with their images in xtherion memory. Next it invokes therion. As a matter of fact you could do without xtherion and call therion from the shell (the command prompt), which is what I do when i want to generate a map from a set of input files, without editing them.

therion processes the input data files and coordinates the work of the external programs [thbook 8]. It reads the input files and interprets the commands in them. First it computes the positions of the stations. In particular it find closed loops and distributes the closure error on the shots.

Next it processes the data of the scraps (files .th2) and transforms them according to the positions of the stations. After this it exports the data as MetaPost files (.mp), and invokes mpost. This program processes the ".mp" files and produces PostScript files (.ps). A small file for each scrap, ie, for each piece of the map.

The PostScript files are processed by therion and converted into a PDF-like format. Then it invokes pdfetex passing it these PDF-like files. This program produces the cave maps in PDF format, taking care of the formatting and the inclusion of texts.