Short-circuit Logic

Nobody nobody at nowhere.com
Thu May 30 21:10:03 EDT 2013


On Thu, 30 May 2013 19:38:31 -0400, Dennis Lee Bieber wrote:

> 	Measuring 1 foot from the 1000 foot stake leaves you with any error
> from datum to the 1000 foot, plus any error from the 1000 foot, PLUS any
> azimuth error which would contribute to shortening the datum distance.

First, let's ignore azimuthal error.

If you measure both distances from the same origin, and you have a
measurement error of 0.1% (i.e. 1/1000), then the 1000' measurement will
actually be between 999' and 1001', while the 1001' measurement will be
between 1000' and 1002' (to the nearest whole foot).

Meaning that the distance from the 1000' stake to the 1001' stake could be
anywhere between -1' and 3' (i.e. the 1001' stake could be measured as
being closer than the 1000' stake).

This is why technical drawings which include regularly-spaced features
will normally specify the positions of features relative to their
neighbours instead of (or as well as) relative to some origin.

When you're dealing with relative error, the obvious question is
"relative to what?".




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