Cavern in Feet

[David A. Riggs]

On 10/23/07, Graham Mullan <graham.mullan at wotcc.org.uk> wrote:
> Ah but which feet do you use, The international foot or the US survey
> foot? I gather the latter is 610 nm longer than the former.
>

Being a nation firmly rooted in science, we've standardized on The
President's foot, a size 10.5 running shoe - it was his idea!  ;-)

Considering that this difference on the longest shot I'd ever consider
taking underground is three orders of magnitude smaller than the most
precise measurement I can make with a fiberglass tape (tenth or
twentieth foot), I'd say that it doesn't matter for a cave survey
which foot is used. The difference would account for a total
cumulative error of less than 4 feet for the entirety of the Mammoth
Cave survey. Should you really care, you could see from the conversion
factor in 'useful.h' that Survex uses the International Foot.

src/useful.h:#define METRES_PER_FOOT 0.3048 /* exact value */

- DR

-- 
David A. Riggs <david.a.riggs at gmail.com>