The city plan of Vienna from 1547/1549 by Augustin Hirschvogel and its 'quadrants'
Cartographica Helvetica 20 (1999) 3–12
Augustin Hirschvogel (1503–1553) produced, among other works, the first planimetric city map of Vienna. None of the three original sketches has survived. However, a copy exists on a round table-top, and there are prints of the map, engraved on six copper plates in 1552.
In addition, there are six instruments similar to a plane table which Hirschvogel called 'quadrants'. Based on these 'quadrants' it was assumed until a few years ago that Hirschvogel had for the first time used the principles of triangulation in surveying the city. The author now refutes this speculation by showing that the point of origin for these surveys were large, irregularly spaced town squares and not the usual towers and spires. These 'quadrants' were therefore not used for the construction of concentric polygonal rings but rather as an aid in training heavy artillery (a predecessor of the azimuth circle). This explains why these 'quadrants' were made of the large town squares: it takes room to fire heavy artillery for defending the positions outside the fortifications. This could also be the reason Hirschvogel called these instruments 'quadrants', even though they were actually a full circle, because 'quadrant' is the name of the instrument used in the military for measuring vertical angles. It is assumed that the use of Hirschvogel's instrument remained theoretical and that it was never actually used in practice. There is also no evidence that there was ever a mill stone marking the center of one of the mentioned town squares from which distances were to have been measured.
The use of quadrants as military aids instead of as a surveying instrument in no way diminishes the significance of Hirschvogel in the development of cartography. He produced a very exact city plan of Vienna and probably used some kind of method of triangulation. With only the circumference and two diagonals of the city, that would never have been adequate enough for making such a good map for military purposes.