In the mid-seventeenth century, sailors in Danish waters relied on foreign charts, especially from Holland, for navigation. These were highly inaccurate and rarely based on scientific surveys of the coastlines and open waters. There was little doubt that better resources were needed.
Jens Sørensen was born in 1646 in Sølvitsborg, Blekinge. He was the son of a well-to-do merchant and ship owner from Bornholm. During the Skåne Wars, the Sørensens were forced to shut down their business and abandon their home in southern Sweden. They moved to Copenhagen in 1677 and later settled in Køge in 1686, where they remained for the following 25 years.
In May, 1689, Jens Sørensen sent a letter to the Danish king that detailed the country’s need for nautical charts, especially in the Baltic Sea region, where only Dutch charts had been developed. This Sørensen knew from 21 years on Danish waters in his father’s and his own trading vessels. He had developed a good working knowledge of the hidden underwater rocks and shallows in the region and drew a preliminary chart as an illustration of his capabilties for the king. With his letter and chart, Sørensen also sent a request for employment as hydrographer. On June 11 of the same year, the Danish king accepted his request.
In the following years, Sørensen worked under King Christian V and Admiral Niels Juel and undertook extensive surveys of Danish waters each summer. He included relevant settlements, depths, reefs and shallows in his measurements. He also frequently took to land to undertake coastal measurements. In the winters, when Denmark’s fjords and straits were frozen solid, he also pursued surveys in these regions.
Jens Sørensen brought passion, diligence and contientious dedication to his work as hydrographer. The resulting charts of Danish coasts and waters reflected Sørensen’s commitment to his work.
Respect for Denmark’s first hydrographer continues to thrive to this day, especially given the simplicity of his tools and the meagreness of his scientific knowledge. Had Sørensen been in the employement of a larger nation and with more abundant resources, he would certainly have earned a place among the most famous hydrographers of his time.