BCRA Grade 5

[Wookey]

On Tue 14 Jan, Thrun Robert IHMD wrote:
> I don't know why the definition was changed.  I was
> not able to find any survey where the surveyors 
> tried to ascertain the accuracy of their measurements.
> My talk in 2000 was the first and only effort to see if
> surveys actually met the Grade 5 requirements.

I don't think that's true bob. I'm sure there have been efforts to quantify
the accuracy of surveys. For example I have analysed a large number of CUCC
calibration readings to try and understand something about the errors in a
survey. (these are not a real survey but because there are  a lot of them
repeated they are a useful test case).

And Larry Fish has run statistical analysis on large surveys to see how
accurate they really are.

I'm sure there have been others. 

> My
> conclusion was that there are no surveys that meet the
> requirements. 

I would not argue with that. Compass readings are nothing like as good as
the BCRA grade 5 requires.

> Surveyors simply called a Compass, Tape,
> and Climometer survey (a clearer term that I prefer) a
> Grade 5 survey. 

People are slightly more discerning than that. They call a CC&T survey that
they took reasonable care over a grade 5 survey. One they took little care
over (or used inferior equipment) they call grade 3, or maybe 4 if they
felt it was somewhere between.

> The revision brings the BCRA Grading
> System in line with actual practice and changes the 
> System from a failed attempt to quantify the accuracy
> to jargon for the sake of jargon.

I was generally with you till this last sentence. I do in fact agree with
you that the BCRA grading scheme is not actually very useful for it's
intended purpose and a simply serves as a shorthand description of the
method and instruments used. An actual description of the instruments and
method used would probably be rather more useful in determining expected
errors.

However this revision does bring things more in line with practice so I do
think that's an improvement, and not just 'jargon for the sake of jargon'.

Wookey
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