Perception among the lettuces

The perception of the human eye is a stunning thing.

Today's project was putting together a herb and vegie garden in the backyard. In the morning, I headed out into the yard with string, pegs and tape measure. I marked out, as well as I could, the dimensions for our new garden bed.

Cara came outside and looked. And looked some more. And squatted down and looked. "It's not square," she said emphatically, noting a discrepancy in the trapezoid layout I had slaved over.

"Well, square's not exactly what I mean - I don't know the word - but it's not right."

Why would I rely on a human eye over the trusty old tape measure? The measure does not lie. But she was insistent. So I remeasured. Bummer. I was out by a full 7 centimetres, just trying to find centre on the baseline against the fence! I'd made a simple mess of some simple maths.

When that mistake became the basis on which I pegged out point 'A', my error was extrapolated over the whole length of the triangle that I had laid out to provide two sides for the garden. Not good.

Cara had no want for tape measures by this stage. She eyeballed it from a distance, moving peg 'A' until she was pretty sure she'd found centre. The distance from the baseline to point 'A' was somewhere over 3 metres.

When she was happy with her eye judgement, we handed the case over to the jury (the tape measure) for deliberation. I can't remember the exact measurements, but if one long side of the triangle measured 312cms, the other side measured 313cms.

In other words, just by eyeballing it, Ol' Hawkeye got an accuracy of within 10mm over 3000mm! Impressive.

I've heard some great woodworkers say that with time and experience they learn to trust their eyes more and gadgets less. I think today's little exercise served to illustrate the point nicely.