General study on Surveying Technology and the Standard in Ancient Japan

2019 Fiscal Year Final Research Report

• Project/Area Number: 15H03264
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Archaeology
• Research Institution: Mie University
• Principal Investigator: OZAWA Tsuyoshi 三重大学, 人文学部, 教授 (00214130)
• Project Period (FY): 2015-04-01 – 2020-03-31
• Keywords: 考古学 / 歴史考古学 / 測量 / 尺度

Outline of Final Research Achievements

By examining how the orientation of large-scale structures in ancient Japan was determined, I found it was not the measurement of magnetic north or the true north using circumpolar stars and polaris, but the measurement of the true east-west direction using the sun. Comparing Fujiwara and Nara capital, the linearity of both roads is fairly good, and there is almost no difference. On the other hand, the accuracy of right-angled drawing at Fujiwara capital is low, which suggests that there was a leap in surveying technology between the two capitals. The large scale and the small scale specified by Taiho Codes correspond to Koguryo scale and the large scale of Tang in order. Koguryo scale probably derived from the back side of the scale of Southern Dynasty in China.

Free Research Field

考古学

Academic Significance and Societal Importance of the Research Achievements

日本古代の方位測定法については誤解が多く、方位磁針や北極星による測定とみる説も散見する。ところが、当時の磁北の偏角（真北からの振れ）は現在より大きく、北極星にあたる星も存在しなかった。太陽による真東西の測定と明示した本研究の意義は大きい。また、藤原京と平城京の間で技術的な飛躍があり、そこで測量技術は一定の水準に達していたことも判明した。このほか、由来をめぐり諸説があった高麗尺を南朝尺の裏目とした点も特筆される。