Passage walls in Survex

[Andy Waddington]

Sometime before sending, footleg typed

> I would propose
> supporting LRUD data attached to a leg. By default take it to be for
> the first station in the leg, but allow an option to specify it for
> the second station in the leg.
> 
> e.g.
> ;From   To   Tape   Compass   Clino   L   R   U   D  stn
> 1          2     5.34    234           -6       0.3 0.4 1.4 0.3
> ;The LRUD data is taken to be for stn 1
> 2          3     4.62    246           -2       0.2 0.2 1.3 0.4   3
> ;The LRUD data is taken to be for stn 3 (specified)
>

OK, so that specifies a cave with three stations and two legs. Clearly
you need to associate not two but THREE sets of LRUD data with those
two legs. How is that going to work ?

It seems to me that the logical way to do LRUD is to specify a station
at which the LRUD applies, then a leg to which the plane of the LRUD
is taken as normal.

So a format that contains information equivalent to:

LRUD at 1 data 0.3 0.4 1.4 0.3 normal 1 2
LRUD at 2 data ............... normal 1 2
LRUD at 3 data 0.2 0.2 1.3 0.4 normal 2 3

would be the way to go. In reality not all LRUD data are taken at
stations anyway - I've often measured LRUD part way along long legs
when passage shape/size is changing. Mainly to inform the translation
of sketching to final drawing, but the data are there and surely we
need to be able to associate them with the place where they were
recorded, even if it wasn't at a station:

LRUD at 1 2.5 2 data 0.7 1.3 0.2 2.0 normal 1 2

for example, to suggest LRUD data at 2.5m from station 1 towards
station 2, and taken in a plane perpendicular to the leg 1->2.

LRUD data are a separate dataset and while each set is associated
with a leg, it is not reasonable to impose a restriction to just
one set of LRUD data per leg.

Andy