Artist: Charles William Carey
Date: 1760
Museum: Naval Museum (Madrid, Spain)
Technique: Brass
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.
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