Loop Closures

[Graham Mullan]

In an email, Olly Betts said:

I'd definitely be interested to hear results of any trials people have done
comparing the newer instruments with the traditional ones.

Anecdote time. Cannot give you the results of a back-to-back test, but... In
Gough's Cave we used both Total Station & Distox/PDA to resurvey a loop that
Willie Stanton had surveyed using a theodolite back in 1979. Willie used
that instrument because he'd been told that the concrete floors had steel
rebar in them. We did not find that a problem but had to use the Total
Station where the passage was lined with steel hand rails. This was about
half the distance, at a guess. Both loops, Willie's and ours, had a
horizontal misclosure of near enough 0.5 m. IIRC in both cases the vertical
misclosure was negligible.

Be interesting to run the same loop using this technology as well as
Distox/PDa and compass/tape/clino.

Graham