Extended elevation, change of height only

[Olly Betts]

On Sat, May 02, 2026 at 10:19:22AM +0100, Andrew Atkinson wrote:
> When doing extended elevation Therion has a command that only uses the
> vertical component of of the leg. This is very useful for legs that cross a
> passage and some avens.
> 
> pp101 of the Therion book
> extend vertical 5 5’

So this seems to effectively rotate such legs to be perpendicular to the
plane of the page, and then project them onto the page (whereas *eleft
and *eright just rotate legs into the plane of the page).

However the orientation of left/right passage dimensions in the extended
survey flips if the leg goes into the page vs coming out of it.  Do you
know how Therion handles that?  I don't see anything in the thbook about
it.

Cheers,
    Olly