BCRA Grades

[Olly Betts]

On Wed, Jan 15, 2003 at 10:11:48AM +0000, David Gibson wrote:
> In article "BCRA Grades" in <!cave-surveying>, on Mon, 13 Jan 2003
> Martin Ellis <mjellis@tesco.net> wrote
> 
> >In the new BCRA Cave Surveying booklet by Anthony Day there has been a
> >change in the definition of a BCRA Grade 5 survey from that given in the old
> >cave surveying booklet.
> 
> AS you might possibly know, Im the editor of a new BCRA magazine -
> Speleology - and issue 1 is due to go to the printers next week.
> 
> Could I use your e-mail message in the letters column?

I'd wait for Anthony's answer first - he is on this list.

I take it this change isn't justified in the book?  If not, that's a
pity.

The change is deliberate.  I read an early draft of the book to spot
problems and offer comments, but I'm not one of the authors.  The
following is my understanding of why the changes were made, but it may
not be quite correct.

The problem is that the old criteria were actually impossible to follow
in general, since it's rare to be able to check the accuracy of all your
survey measurements.  To be sure all measurements are accurate to within
the stated limits, you'd really need to have every leg in a loop.

So in reality people claim survey grades according to the methodology
they use - someone surveying with a calibrated sighting compass and clino, 
a reasonable quality survey tape, and taking care to relocate survey
stations will probably claim grade 5.  And that's not actually
particularly unreasonable.

It therefore made sense to amend the grades so they describe the
methodology followed rather than the results achieved, as that's
actually easier to know for the surveyor, often more useful to computers
and humans reading the data, and reflects widespread current practice.

Cheers,
    Olly