[Therion] Which line are LRUDs perpendicular to?

12 Dec 2015

      Hello everyone -

The recent discussion about LRUDs brings up another question I have.  Take 
some example data ...

========
  data normal from to tape compass clino backcompass backclino left right up 
down

# Main survey shots
  A1 A2  8.4 72.5 -52 252 +53 3 5 3 6
  A2 A3  6.7 67 -10 248 +10 2.2 1 2 1.4
  A3 A4  48.0 28 +2 208 -1.5 4 5 0.7 1.1
========

For each shot the LRUD data is taken at the "to" station.  Does Therion assume 
this data is perpendicular to the line going to the next station?  Or is it 
perpendicular to the line coming in from the previous station?

At station A2 - Does Therion treat the LRUD data as perpendicular to A1-A2 or 
as perpendicular to A2-A3?

Thanks - Bill Gee