Inō Tadataka’s First Survey in Ezo

Inō Tadataka left Edo in June 1800 with a six-person survey party. He had studied astronomy under Takahashi Yoshitoki and wanted a better measure of the distance corresponding to one degree of latitude. Surveying the northern route also served the government’s interest in mapping Ezo, a region already inhabited by Ainu communities.

The party traveled north through Honshu and crossed from the Tsugaru region to Hakodate. It then measured along Ezo’s southern and eastern coast, reaching Nishibetsu in August. This itinerary covered a selected coastal route, rather than the whole island. The approaching winter helped determine the return, and the party reached Edo in December after roughly half a year away.

Measured distances and directions joined astronomical observations in the resulting survey work. The journey began the sequence that later extended around much of Japan’s coastline. Its immediate achievement was a body of route measurements and coastal information; the completed national map belonged to later surveys and posthumous compilation.