The Duisburg town plan of 1566 by Johannes Corputius and his surveying methods
Cartographica Helvetica 11 (1995) 2–10
Thanks to two hand-drawn survey sketches (Library of the University of Heidelberg) it is possible to retrace the construction method of the famous town plan of Duisburg from 1566. It is the work of 24-year-old Johannes Corputius (1542–1611) from Breda, who studied mathematical science under Gerard Mercator at the Gymnasium of Duisburg beginning in 1562.
Corputius first calculated the position of the meridian and drafted it through his initial base, the tower of the Salvator church. From there he surveyed the next positions, from which he measured the angles of a number of dominating spots like towers of the surrounding town wall. His two sketches show the bearings and their accurate total sum of 360 degrees, not correct is their graphic representation (plotted onto 140 degrees).
The computer-assisted reconstructions represent the positions of the 28 features which Corputius used as a basic grid for his town plan, providing a perfect 'bird's-eye view'. We do not know the exact method he used to map the streets and buildings, but we can assume that he measured them conventionally by means of counting footsteps. Presumably also other town plans of the 16th century had been drawn up by this or a very similar method.