A Geographical Study on the Accuracy of the Inoh's Map, the First Scientific Map of the Whole Japan (1821)

Authors: Yuki Iwai*, Graduate School of Life and Environmental Sciences, Univ. of Tsukuba, Yuji Murayama, Professor Emeritus, Univ. of Tsukuba
Topics: Historical Geography
Keywords: Inoh’s map, Historical map, Spatial analysis, GIS, Japan
Session Type: Virtual Paper
Day: 4/11/2021
Start / End Time: 8:00 AM / 9:15 AM
Room: Virtual 24
Presentation File: No File Uploaded

The history of modern maps in Japan began with the Inoh’s map made by surveying the whole of Japan on foot 200 years ago. The Inoh’s team investigated not only the coastlines and major roads but also various geographical features such as rivers, lakes, temples, forts, village names, etc. The survey was conducted successively ten times from 1800 to 1816.
The Inoh's map is known as the first scientific map in Japan by the same systematic method. However, we have to note that only 75% of the coastlines were measured by actual survey, and the remaining 25% were drawn by the estimation. In this study, focusing on these non-surveyed coastlines, an attempt was made to analyze the accuracy from the viewpoints of geographical distribution and the shapes of the estimated coastlines, the gaps with the actual coastlines, and the causes producing the differences. We used the Digital Inoh’s Map Professional Edition with the geometrically corrected map and the vector data of coastlines in the GSI (Geospatial Information) map.
The analysis showed that 38.6% of the non-surveyed coastlines were cliffs, 25.7% were rocky beaches, and 6.2% were wetlands (including rice fields and tidal flats). We found that there was a significant difference between bays and capes in the accuracy of the distortion. Monotonous linear sandy beaches were accurately traced without a survey.
From the methodological point of view, we conclude that geospatial analysis using GIS is a useful tool to find the geographical distortion pattern quantitatively.

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