In the year 1730 the Norwegian Army surveyor Thomas Hans Henrik Knoff was sent to Iceland by the Danish government to continue and complete the work of Magnús Arason who had been instructed to survey the whole of the country but died before the work was finished. The purpose was to make a precise map of the country once and for all.
Knoff began work immediately after his arrival in Iceland and carried on for five summers. He had by then completed the work left undone by Magnús and corrected his maps to some extent, where it seemed necessary. He had also made seven maps of specific districts and an overall map of the whole country which he finished in the year 1734. When the maps were brought to Copenhagen an amazing dispute began over them. Knoff had sent a copy of some of them to his superior in Norway. Some regarded this as quite outrageous if not actually treasonable. The Danish king put an end to the dispute by deciding that the maps should not be displayed or made use of. Their fate was thereby decided, and they were put away under lock and key in some government department, where they lay unpublished and forgotten by nearly everyone for many years.
In 1752 the Danish scholar, Niels Horrebow, published his book about Iceland entitled Tilforladelige Efterretninger om Island. He had been sent to the country to explore it and enquire into the state and prospects of the people. The book was accompanied by a map of Iceland. This time it is not the old version by bishop Gudbrandur Thorláksson which is used as a basis, but an entirely new departure, the Knoff map of 1734, which was now brought out of some cabinet and dusted off.
The map is altogether rather careless and poorly done. But in spite of various obvious flaws, its publication was the most important stage in the history of the cartography of Iceland since the appearance of bishop Gudbrandur's map more than 150 years earlier. For the first time the public was given a chance to see a map of Iceland which to some extent was based on triangulation and proper surveys of the country, even though in many places rather too much shot through with slipshod observations, guesses, or even fantasies. The book was published in German (1753), English (1758), and French (1764), a copy of the map accompanying all of them. Longer or shorter extracts from it appeared in various collections of voyages during the decades following, including Histoire générale des voyages (1779) by A. F. Prévost which also had a copy of the map.