Quoting Bill Chadwick <W.CHADWICK@sky.com>:
As this is quite a nice way of presenting cave surveys, perhaps a Google tile generator would be a good add on for Therion. The advantage of building the renderer into Therion would be that the overlay could be drawn separately for each Google Zoom level to achieve a good line width and text size.
Hmmm. Just one problem. Therion it self does not have any build-in bitmap generator. All maps are generated as vector PDF. And generation of bitmaps from PDF is very tricky (currently only Acrobat reader is able to render these PDF files 100% correct).
I am well informed in the areas of coordinate systems and map projections and able to program in C++. With some guidance I might be able to help with the coding of such an extension.
I have tried to generate Google Earth's KML files from therion and it seems to work (scrap outlines for maps, centerline for model, try latest developement snapshot). All you need is to have georeferenced cave data (see "Coordinate Systems" in thbook). Then just export model -fmt kml will generate .kml file readable by Google Earth. If somebody will create a good rasterizer script for PDF files generated by therion (using ghostscript or acroread), there is no problem for us to add export of long-lat coordinates together with PDF file to be used by this script. S.