Dan Similarly to Martin I do all my image overlays (topo image, aerial photo, geology, contours, property boundaries, map gridlines etc) in a standalone GIS package, then use the result as jpg surface overlay in Therion.
Therion can then regurgitate it all with the cave included as a stand alone image, or you can produce geo-referenced cave shapefiles from Therion that will snap straight into your GIS project without ever having to load the image into Therion in the first place. Which is the best way depends on what you want to do ultimately, and which application you feel most comfortable using. If you need a more detailed example than Martin has provided I can pull together a cut down example in due course. I appreciate that the hardest bit is knowing how to organise the Therion data. After 3 years I am still having new insights and have no idea if I am doing it well. Bruce
