Survex 1.0.21 released

[Olly Betts]

On Mon, Nov 18, 2002 at 09:00:30AM -0700, John Halleck wrote:
> On Sat, 16 Nov 2002, Olly Betts wrote:
> 
> > * cavern: if "*infer plumbs on", don't infer a plumb if the clino is
> >   +/- 90 degrees, but the backclino isn't (and vice versa).
> 
>   I guess I'm missing something.
> 
>   What does it mean if the inclinometer reading is 90 degrees but the
>   back inclination is not 90 degrees.

I assume you mean "-90" for the backsight...

It means that the user actually read 90 degrees on the clino, rather
than writing 90 to mean that they plumbed the leg.  At least that's the
new assumption Survex makes.

Survex only infers plumbs in this way if you specifically tell it to, or
when reading Compass data.  The Compass format Lech data set has a leg
with 90 forward and 0 back - clearly bogus, but it got me thinking about
the check and I realised it could be a problem in some reasonable cases.

>   (I.E. When do you meaningfully get this case?)

If the forward clino overreads by 3 degrees, and the backclino
underreads by 2, then on an 87 degree leg, the forward clino would be
90, and the back -85.  It would be better to plumb in such a situation,
but by the time you have the data back on the surface it's a bit late.

Before Survex would assume the 90 meant a plumb, and then give an error
because the backsight wasn't a plumb.  It's not a common situation - if
it was someone would probably have reported it by now.

Cheers,
    Olly