Pentaprism in Surveying
In surveying a double pentaprism (two pentaprisms stacked on top of each other) and a plumb-bob are used to stake out right angles, e.g. on a construction site.
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Famous quotes containing the word surveying:
“As for my own business, even that kind of surveying which I could do with most satisfaction my employers do not want. They would prefer that I should do my work coarsely and not too well, ay, not well enough. When I observe that there are different ways of surveying, my employer commonly asks which will give him the most land, not which is most correct.”
—Henry David Thoreau (1817–1862)