 His method of visualising planes of water level to illustrate contours of depth (isobaths) in his map of the Merwede (1728) was the first of its kind.He was an advocate of pumping out the Haarlemmermeer (Haarlem lake), which was done a century after his death.He became a surveyor at the age of 19 and began to draw maps, a lucrative job in his day.