Steve I'll be interested to see if anyone has managed to create a ground line as you describe. I assume it is not possible to make it a boundary for the background colour.
I have just tried taking a 3d gps trail with 2m resolution and then including it as a survey line and this can be included to give context in Loch, Aven and pdf outputs. Not sure how well it would work with extended elevations though - I have only tried it with projected elevations. It adds interesting context to plans and elevations, but best with a white background in elevations. It is quick to produce, but seems a little clunky. If anyone has a better way to include gps trails in therion data I would like to learn of it. Some snippets below to show what I mean. Bruce centreline cs lat-long grade BCRA3 walls off # 3D model auto = only use LRUD if no scrap available # on off mark temporary flags surface #do fixed stations inherit shot flags? # station-names 4wd01 [] # to avoid name clashes if required fix 1 -42.0001724 171.9024155 572.6 fix 2 -42.00020492 171.9022789 574.04 fix 3 -42.00021414 171.9021513 574.04 fix 4 -42.00026879 171.9020413 575.01 fix 5 -42.00030752 171.901925 575.01 #thousands of these, they are decimal degrees and metres data nosurvey from to 1 2 2 3 3 4 4 5 5 6 6 7 #thousands of these as well, a spreadsheet makes them easy to generate #Then just select this survey along with your cave when processing
