[Therion] Main route through a cave

[Bruce Mutton]

> I am surveying a cave that could be best described as an insanity of hidden routes.
> When you go through the cave, it feels easy. You follow the obvious route... This means that the survey is harder to navigate than the cave itself.

Welcome to my world.  Have not solved the problem yet but it is one I will need to come back to when we finish surveying.
Where there are multiple levels it is relatively easy just by having a map per level and offsetting them.  Maybe preview above/below the secondary passages to maintain context.
Where there is frequent interconnection of say 5 levels, as we have in a few places, it becomes a nightmare.  Especially when there are no blank places to offset the passages to.
Andrew's suggestion of a 'main route map' is what we have considered, but have not figured out how to do this without either duplicating map structures or rebuilding our entire map structure.  Neither sounds like fun.
Axel's suggestion of a special line type for plotting the track you take through the cave is a partial solution, where the offsetting is not too complex.  I have a least one example where I think our map will still be unintelligible.  That perhaps points to my choice of map subdivision being suboptimal I suppose.

Bruce