<Martin wrote

>The original idea of Therion is that "survey" represents one survey trip. … So it is not the best idea to manipulate with surveys. 

I agree Martin, one survey file, one trip.  However we just did a survey of three small multi-entrance caves and overland surveys over a couple of days.  In hindsight we were a bit messy in practice as we surveyed into one cave and out of another entrance and into another cave, then back out to the first cave etc etc. 

What I found was that Therion could not (or I could not get Therion to) adequately resolve the statistics for the caves individually until I split some of those surveys into two or three.  It also would not separate surface survey statistics from cave statistics (but I think that is a bug).  Statistics are resolved correctly for maps but not for survey-list.

So as a last resort I cut the survey trips into multiple surveys/files.  If I had drawn the scraps before doing this I would have had a difficult job patching it all back together.  An unusual situation perhaps, but one where manipulation of the survey files was able to lay a better foundation on which to build scraps and maps.

Bruce