Adriaan Anthonisz

Adriaan Anthonisz (also known as Adriaen Anthonisz of Alcmaer) (1527–1607)^[1][2][3] was a Dutch mathematician, surveyor, cartographer, and military engineer who specialized in the design of fortifications. As a mathematician Anthonisz calculated in 1585 the ratio of a circle's circumference to its diameter, which would later be called pi.^[2]

Statue of Adriaen Anthonisz by John Bier [nl]

Life

Anthonisz served as burgomaster (mayor) of Alkmaar in the Netherlands from 1582.^[4]

Adriaan fathered two sons, and named them both Metius (from the Dutch word meten, meaning 'measuring', 'measurer', or surveyor). They each became prominent members of society.^[5] Adriaan Metius (9 Dec 1571 – 6 Sep 1635) was a Dutch geometer and astronomer. Jacob Metius worked as an instrument-maker and a specialist in grinding lenses and applied for patent rights for the telescope a few weeks after Middelburg spectacle-maker Hans Lippershey tried to patent the same device.^[6]

Career

In 1585 Anthonisz discovered that the ratio of a circle's circumference to its diameter, later called pi, approximated the fractional value of ⁠355/113⁠. His son Adriaan Metius later published his father's results, and the value ⁠355/113⁠ is traditionally referred to as Metius' number'.^[7][8]

He is regarded as one of the first military engineers to apply the principles of the Dutch fortification system.^[9]

Some of his professional accomplishments included mapping the Berger lake and expanding and fortifying Naarden and Muiden.^[10]