Protractor

This instrument was used to calculate inaccessible distances and heights, measure horizontal angles, draw charts or topographic maps, and make trigonometric calculations.

It has a semicircle calibrated from 0 to 130 degrees with a cut-out center. An alidade rotates around a small cut-out circle. The base is bordered by a graduated ruler used to mark minutes on the edge and note down the angles from topographic measurements. To create charts, it was used on a board of approximately one meter square, supported on a tripod, on top of which the paper that was to be drawn on was laid.