[Therion] Aligned cross sections for multiple passages

[Tarquin Wilton-Jones]

> I would like to do cross sections of multiple passages that are aligned
> according to each other. I can see how to do multiple cross sections,
> and presumably I can manually shift them into positions and hope I get
> it right. But is there a way to get Therion to place them all relative
> to each other?
> 
> As an example, I have used the effect here with a bitmap-rendered
> survey, done manually:
> http://www.cavinguk.co.uk/info/cresSurv/CrescentFinalOverlap.gif


I have an idea that might just be crazy enough to work. If only I could
get Therion to output an XVI file containing the stations and splays I
am interested in.

Imagine there are three parallel passages, running over the top of each
other. I know I want a cross section of all three passages at once; at
station 12 in the top passage, station 78 in the middle passage, and
station 5 in the bottom passage.

source "cystanog.th"
select 12 at toppassage.mycave
select 78 at middlepassage.mycave
select 5 at bottompassage.mycave
export map -projection [elevation 355] -fmt xvi -output "test.xvi"

If only this worked (it doesn't - you can only select a map or survey,
not a single station), I would have the positions of all three passages
relative to each other. I could then use those positions to place the
cross section scraps for each passage, and include that as a scrap in
the overall cave map.

So ... can I get Therion to output just those 3 stations - and
optionally their splays, projected on a bearing?

(I am thinking that yes, I could make a subsurvey for each of these
stations, equated to the parent survey's station with the same number.
Then use "select" with the subsurvey's name. But this is so very messy,
and I was hoping for a cleaner solution, that didn't require
modification of my source data.)