stadia mark (Q1229407)
crosshairs on the reticle of a theodolite or other surveying instrument
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Current Data About stadia mark
(P18) Image Provided By https://upload.wikimedia.org/wikipedia/commons/c/ca/Baak.svg

(P373) Stadia marks

other details
aliases stadia lines
 stadia hairs
description crosshairs on the reticle of a theodolite or other surveying instrument

External Links
(P646) /m/02z23gr