The Measurers:
a Flemish Image of Mathematics in the Sixteenth Century

Figure 30
The use of the shadow square or geometrical quadrant on an astrolabe, simple theodolite or Holland circle.

Bearings taken with the shadow square (see figure 29) after transfer on to a plan drawn to scale.
Gemma Frisius, De astrolabo catholico (Antwerp, 1556) (catalogue no. 3).

See also figure 29
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