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News Navigator: Who was Ino Tadataka?

A statue of Ino Tadataka is seen at Tomioka Hachimangu shrine in Tokyo's Koto Ward on May 7, 2018. (Mainichi)

The Mainichi Shimbun answers some common questions readers may have about Ino Tadataka, who walked around Japan in the Edo period to make the first surveyed map of the country. How did he conduct the survey and create the map?

Question: Who made the first surveyed map of Japan?

Answer: Ino Tadataka made the first surveyed map of Japan. This year is the 200th anniversary of his death. He was born in Kujukuri, Chiba Prefecture, in 1745, and was adopted by the Ino sake brewer family in Sawara when he was 17 years old. He successfully headed the business, and retired at the age of 49. He then studied astronomy in Edo (now Tokyo).

Q: Why did he start the survey?

A: Ino wanted to know how large the Earth was by measuring 1 degree of the planet's latitude. He tried to calculate it by measuring the distance between Fukagawa and Asakusa in Edo, but the margin of error was too high. Thus, he decided to try to measure a longer distance. In 1800, he got permission from the Tokugawa Shogunate to survey and map the island of Ezo, now Hokkaido, where Russian ships often appeared. Ino was 55 when he set out on his first trip.

Q: How did he carry out the survey?

A: On his first trip, Ino counted his own steps. It is said that his stride was approximately 70 centimeters. From his second survey conducted the following year, ropes and iron chains were used. Astronomical observations were also used to measure the latitude of locations. The survey team spent 17 years walking around the whole country. They traveled a total distance of about 43,707 kilometers, which is even greater than the circumference of the Earth.

Q: How was the map created?

A: Based on the data collected, the team made a scale and poked pinholes at the corners of each surveyed section. They then connected the dots with ink to produce an outline. That draft was layered on map paper, and the pinholes in the draft were inserted again with needles. Next, the survey lines were copied by connecting the pinholes with red lines. Place names and depictions of scenery were added as finishing touches. The maps of targeted areas were constructed for almost every survey, but the final version of Ino's work, which amounted to 225 pages, was finally submitted to the shogunate in 1821 -- three years after his death.

(Answered by Noburu Hirose, Cultural News Department)

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