How to deal with LRUD data?

[Mike McCombe]

At 14 February 2005 13:13 Philip Balister wrote

> 1) LRUD is a station attribute, not a shot attribute. So the LRUD data
> is unique to the station. Survex already treats shots and stations
> separately, so it is in good shape to handle LRUD without the extra shot
> hacks needed by some other cave survey packages.
> 
> 2) Once you have the LRUD data associated with the station, you face the
> problem of what direction the vectors point. In normal cases, LRUD is
> roughly normal to the passage bearing. However, at bends and junctions
> LRUD become almost meaningless. To be consistently useful for map
> drawing, the LRUD data should include a normal vector that defines the
> plane the data was taken in.

I have always taken the LR components of LRUD data to be referenced to an
ordered pair of stations. This pair does not necessarily correspond to a
survey shot. When using LRUD data to define the walls of a passage, one
needs to define an ordered sequence of stations, which will again not
necessarily correspond to a sequence of survey shots. (If leap-frogging is
used, it certainly won't!)

Mike McCombe