2020 Volume 129 Issue 2 Pages 227-240
The map of Japan drafted by Inoh Tadataka is considered to be the earliest produced from a scientific survey. The descriptions of longitude and latitude are based on astronomical observations, and Inoh's nationwide survey has been considered to be the origin of modern surveys in Japan. However, he did not succeed in determining longitude. Although he had knowledge of a spherical earth, the results of his survey were projected on a plane, not on a spherical surface. The parallels of latitude drawn on his maps are based on an accurate astronomical survey he carried out, but the meridians on his maps are absolutely inconsistent. His survey method also combined traverse and intersection surveys without control points. Therefore, his nationwide survey cannot be considered to be representative of a survey carried out in the modern period. There are many open traverse lines on his maps. These lines generally extend to temples and shrines, although they are not effective for improving the accuracy of the survey. Because temples and shrines might have been important public facilities at that time, the Tokugawa shogunate government probably requested information concerning their locations. He carried out a nationwide survey ten times, but he could not survey the northern half of Ezo island (Hokkaido). It is said that Mamiya Rinzo, who studied survey technology under Inoh Tadataka, surveyed Ezo island and submitted his survey data to Inoh Tadataka, therefore, Inoh's map of Ezo island might be entirely based on Mamiya's data. Further studies are necessary because Mamiya's survey has not been clarified.