# LRUD (was Re: Survex digest, Vol 1 #136 - 3 msgs)

**Paul Fretwell**
paul.fretwell@accelrys.com

*Fri, 3 Aug 2001 15:26:27 +0100*

>>* LRUD are dependant on a shot but there are three ways they can be taken:
*>>*
*>>* - perpendicular to next;
*>>* - perpendicular to last;
*>>* - average between last and next.
*>*
*>*There's more than that - for instance, some people take them "across the
*>*passage". Roughly speaking this means that the L/R line is perpendicular
*to
>*the passage wall where it intersects. It's actually the obvious distance
*>*for someone to measure when you ask "how far is it to the left wall", and
*it
>*can be more useful when drawing the survey by hand. Harder for the
*computer
>*though...
*
Surely what you need is a definition of the vector which is perpendicular to
the plane of the LRUD data? So you could just take the co-ordinates of the
survey station, enter a bearing and inclination to define the vector, and
then the LRUD distances. If this was implemented internally then the
application could use one of a range of behaviours to default the bearing
and inclination of the vector so that switches could be used for 'From
station', 'To station', 'Average of From and To stations' or 'Custom' for
planes perpendicular to a wall where the bearing and inclination of the
vector have to be entered manually?
Footleg