Cartographer Ino Tadataka (1745-1818) was 55 years old when he set out on his first surveying trip in 1800 to chart the coast of Hokkaido.
Accompanied by five assistants, Ino took the Oshu Kaido route to reach the present-day town of Betsukai in eastern Hokkaido. The 3,200-kilometer round trip, accomplished entirely on foot, took 180 days.
I am about the same age as Ino was at that time, but I barely manage to walk 10,000 steps a day on my way to and from the office. I can only marvel at Ino’s fitness.
Ino kept his step length at a uniform 69 centimeters, based on which he calculated the distance he covered during his first surveying trip. On slopes, he used a quadrant to determine the grade and consulted a function table to obtain the planar distance.
None of Ino’s maps showed the elevations of mountains. But he must have felt that Mount Fuji was special: An estimate he made (in the traditional Japanese unit of length) from somewhere near Yui in Shizuoka Prefecture was said to be equivalent to 3,733 meters.
Nobody needs to be reminded today of the astounding precision and accuracy of his completed map of Japan. Nevertheless, I was stunned anew to learn that until as recently as the Showa Era (1926-1989), Ino’s map was still used as reference material for 1:200,000 topographic maps of Yakushima Island and elsewhere.
This month, a little over 200 years after Ino’s feat, the Geospatial Information Authority of Japan (GSI) updated the elevation data of all triangulation stations and benchmarks around the nation.
This was prompted by GSI’s recent switch to satellite-aided surveys from its traditional method of updating data through repeated surveys. Under the old method of surveying, it took more than 10 years to correct discrepancies in topographic data resulting from earthquakes and other phenomena. This process used to require surveyors to literally crawl on the ground like inchworms to take measurements.
As a result of the latest update, the elevation of the triangulation station on Mount Fuji rose by 5 centimeters–from 3,775.51 meters to 3,775.56 meters. This just makes me happy, never mind why.
April 19 is “Chizu no Hi” (map day) in Japan. The day on which Ino set out on his first surveying trip on the traditional lunar calendar falls on this day.
The weather forecast says today’s high temperature may reach a summery 25 degrees in various parts of Japan. I might grab a map and visit a town I’ve never been to before.
–The Asahi Shimbun, April 19
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Vox Populi, Vox Dei is a popular daily column that takes up a wide range of topics, including culture, arts and social trends and developments. Written by veteran Asahi Shimbun writers, the column provides useful perspectives on and insights into contemporary Japan and its culture.
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