From the Geospatial Information Authority of Japan (GSI).
Tadataka was born in 1745 in what is now Kujukuri. At 17 he married into the Ino family of Sawara and took the name Tadataka. At 36 he became a village head.
At 49 he handed the headship of the family to his eldest son and retired. At 50 he moved to Fukagawa in Edo and became a pupil of Takahashi Yoshitoki.
Astronomy at that time could not predict when eclipses of the sun and moon would happen. To solve this, people needed to measure the distance of one degree of latitude and fix the size of the Earth.
Takahashi Yoshitoki planned to find the latitude of many places while making maps, and to work out the length of one degree. He asked the shogunate to allow a survey and map-making as far as Ezo (Hokkaido).
In 1800, at 55, Tadataka set out on his first survey, of Tohoku and southern Hokkaido.
In 1804 he presented a map of the eastern half of Japan’s coasts, which the shogun Ienari viewed. After that he worked for the shogunate. The surveys went on to the Kinki and Chugoku areas, Shikoku and Kyushu, and the tenth survey, of Edo, was in 1816. Tadataka did not join the ninth survey, of the Izu Islands.
Tadataka died in 1818, at 73. His pupils carried on the work, and in 1821 the Dai Nihon Enkai Yochi Zenzu was finished and presented to the shogunate.
It has 214 large sheets, 8 medium sheets (1:216,000) and 3 small sheets (1:432,000), made from surveys over 17 years. The year 2021 was the 200th year since the map was finished.
There is no single right answer. Talking it over with someone at home is a good way to learn.