My reading of the Therion Book suggests to me; - that 'source' specifies the files that Therion should read and process before deciding what to export. The source files should contain or reference surveys and or a surface. - that 'select' chooses which survey(s) and or map(s) from the above files to export. If there is no 'select' statement then 'all' are exported. My interpretation #1 is that this should allow all the surveys of a large (or modest) system of cave passages to be referenced by way of 'source' so that all the survey loop and scrap join distortions can be processed BEFORE Therion decides what to export. This is what seems to occur. So far, so good. My interpretation #2 is that when a map or maps for any particular projection is 'selected' then ONLY the data that relates to those maps should be exported. This is what seems to happen for Map outputs (pdf and ?kml) and Atlas outputs. I have some difficulty and confusion with outputs that don't have a projection, such as the lists, 3d outputs and database. What seems to happen is that regardless of the 'selected' maps, all of the 'sourced' data is exported to this type of output. What I would like is that only the data related to the 'selected' maps are exported. This way all subset outputs can be consistent (same loop closure distortions applied), and separately exported. In writing this out I suspect I may have realised the answer to my question (but not yet tested it). Perhaps what I need to do is 'select' survey(s) that encompass the same part of the cave as the maps? Any insights or clarifications gratefully received. Bruce