@aartaka The statement 'This may sound a little outdated, but this system was perfected to such an extent that in the second half of the eighteenth century it was almost as accurate as the present-day GPS.' remains me of the discussion on mapping in "The Ring of Truth" by the Morrisons in the late 1980s. The image from the book, https://archive.org/details/ringoftruthinqui00morrrich/page/138/mode/2up?q=gps compares a 1798 position (off by 8 miles), the 1980s position using old methods, and GPS (within 50 feet). Video at https://archive.org/details/TheRingofTruth/Ring.of.Truth.S01E03.Mapping.1987.VHSRip.AAC2.0.x264-rattera.mp4 .