Therion is becoming more and more integrated with geographical data manipulation programs, and in particular GIS systems.

Therion can import surface bitmaps (properly georeferenced) and display them in the output, overlaying the cave map on the cartography.

The 3d models exported by therion makes it nicely integrates with 3D viewers and GIS programs.

Cave plots and 3D models can be composed of several "unrelated" entities: different caves, surface aerial photos, digital elevation models, cartographic maps. To put them together so that they fit in the right place we must properly reference them, ie, specify how they place in a "reference system". To this extend we use the command cs (coordinate system). Different coordinate systems can be used for different entities, because Therion knows how to transform from one reference system to the other. Except for a very special reference system, the "local" reference: if no coordinate system is specified, Therion assumes that the data are in the "local" reference. This is like a "floating" refrence which has not yet been related to the other geographical reference systems. It's ok to use the local reference as long as no entity has a cs.

The cs command can appear in

• centerline to specify the reference system for fixed stations
• surface to specify the reference of the elevation grid points
• import to specify the reference system of fixed stations in the imported data
• layout toi specify the reference system in the output layout.