[Therion] Extended elevations with survex data

[John Pybus]

Hi,

I'm trying to create an extended elevation of a cave.  I have the 
centreline data as survex files and have created an extended version of 
the .3d using the survex "extend" command with a specfile to specify at 
which points the elevation switches direction.

I have created a .th file like so:

survey texa-elev

   import texa_extend.3d


   input elev_top.th2

endsurvey

but therion doesn't respect the changes of direction in texa_extend.3d 
and extends it all out to the right which doesn't correspond to the 
drawings in elev_top.th2 and produces very corrupted output.

Is there a way to correct this and tell therion where the switches in 
direction are?

Cheers,
John