The organization of surevys and drawings becomes quickly an issue when the cave is of some length and complexity, or when there are may caves.

Even in a complex cave it is possible to identify "regions" of the cave. These can be used as a basis for a hierarchical organization of the data (survey and scraps) as well as the work. The placement of the therion files and the auxiliary files in the filesystem can reproduce this heirarchy.

At the lowest level there are directories for single surveys, containing the survey scraps and auxiliary files (images etc.). Each directory has a thcoinfig file that can be used to compile the survey map. The scraps should be collected in maps and these merged into the map for the survey, with the joins among scraps that can be defined at the level of the survey. The work at this level focusses on the drawings, and other details (name of the surveyors, fix stations, etc.)

Going up one level in the hierarchy, there is the cave region, which collects individual surveys, with the equates and the joins for the scraps. At this level there are also maps that collect the individual survey maps. Therion thconfig files allow to produce as output the maps aof the cave regions. The work at this level focus on merging the the single survey maps, resolving the overlaps for the best presentation. At times it is necessary to go back to the previous level to implement changes that improve the output.

One step further up there is the cave. The structure and the work is similar to the second level. At times three levels are not sufficient and other imtermediate levels become necessary. On the other hand if the cave is not too big two levels are enough. As a rule, two levels are sufficient for a 1-Km cave, three are necessary for 6 Km cave, ...

When you put together many caves in a system project, you need to go up one further level. This level is usually simple, however, as the cave fix points are already in the cave surveys, and the cave surveys are usually independent. If this is not the case, there arises the need to introduce joins and solve mergings as for the previuos levels.

It is possible to set up different parallel hierarchies sharing the same underlying levels, each hierarchy customized for a particular output. The management of multiple hierarchies might have problems, due to the need to propagate changes and updates to all the hierarchies.