Very good, Kent. Now answer this one:
547.34' * 1.9' = ?
Stephen
> Very good, Kent. Now answer this one:
>
> 547.34' * 1.9' = ?
1040 s.f +/- 30 s.f.
or
0.024 ac.
My point is that the answer is 1039.9' but, by Sig. Digits it is constrained to 2 significant figures. 1040 seems the most logical but that is 3 sign. digits.
Stephen
> My point is that the answer is 1039.9' but, by Sig. Digits it is constrained to 2 significant figures. 1040 seems the most logical but that is 3 sign. digits.
Well, 1040 s.f. is still a better estimate of the product than 1000 s.f. is. That's assuming that the only source of uncertainty in the measurement is due to rounding, of course, which is seldom the case in actual surveying practice.
When you consider that the rounding uncertainty in that 1040 s.f is +/-30 s.f., that is less uncertainty than would be consistent with rounding to the nearest 100 s.f.. So rounding to the nearest 10 isn't really so odd.
I'd say that using significant figures as a way of expressing uncertainty in some quantity derived from survey measurements is not the best solution. That method of expressing uncertainty really belongs more to an era when everyday use of least squares adjustment software with analysis of propagated uncertainty was not feasible and when surveying equipment and techniques commonly used in surveying were much less refined.
