Refers to marking center lines and reference lines, which are required to carry out construction or installation work. In Japan, thin threads wetted with 墨 are often used for marking, hence the term 墨出. Although modern alternatives such as laser marking are currently available, the traditional 墨-wetted thread marking method is used very widely even now.

すみだし
墨出し 壁や柱、床などの中心線の位置や仕上げ面の位置などに印をつけることです。昔ながらでいけば当然、墨でつけます。親墨というのは座標の原点のようなもので、芯から1 mとか離してx方向、y方向に書きます。そこから子墨を出して、壁とか、柱の位置を示す線を描きます。陸墨というのは壁に水平の位置を示す線を描くものです。通常、床の仕上げ面から1 mとか上に出します。「出す」には算出する意味と描くという意味が複合した意味があるようです。
http://www.watanabesato.co.jp/pavements/knowledges/cod_.html

I am probably wrong, but this is just my input to your question.

The measuring part is called surveying. You may have seen guys with those funny tripods. They have laser sights mounted on those.
Then there is physical marking of the boundaries or building foundation dimensions.