Inoh’s map is the first scientifically surveyed map of Japan. Inoh Tadataka (1745-1818) started his nationwide survey over ten times from 1800 and the maps of his results were compiled and submitted to Tokugawa Shogunate Government in 1821 three years after his death.

His motive of the nationwide survey was to get the latitude distance. He drew the map of Japan based on the latitude distance obtained by his survey. His method of survey was traversing, intersection and astronomical observing. We can know his method briefly from the explanation record left by Watanabe Shin who was one of his best pupils. Afterward Ohtani Ryokichi wrote the voluminous work in 1917 about Inoh’s achievements based on Watanabe’s record, Inoh’s maps and his existent survey instruments, and Hoyanagi Mutsumi compiled famous work in 1974 about the scientific technology of Inoh’s survey and mapping.

These two classical studies on Inoh’s achievements, namely INOH TADATAKA written by Ohtani Ryokichi and A NEW APPRECIATION OF THE SCIENTIFIC ACHIEVEMENT OF INÔ-TADATAKA WHO ESTABLISHED A LANDMARK IN THE HISTORY OF LANDSURVEY AND CARTOGRAPHY OF JAPAN edited by Hoyanagi Mutsumi, have variously influenced and been commonly accepted on the studies of Inoh’s survey and maps since then,

Although Inoh’s original maps submitted to Tokugawa Shogunate Government were burnt out in 1873, some duplicates are existing still now. Taking the opportunity of two hundred years anniversary from the commencement of Inoh’s survey, some new Inoh’s maps were found out and bibliographical studies on Inoh’s maps have much progressed. However, scientific cartographical studies have not so much progressed yet.

As for the scientific cartographical themes, the four subjects such as 1) Latitude distance, 2) Inoh’s survey method, 3) Map projection and 4) Mapping process are discussed. Concerning these subjects, the author introduces the commonly accepted views, which are based on the two classical studies of Ohtani and Hoyanagi, and introduces newly reconsidered theories by Nogami Michio. Nogami denied the commonly accepted views and emphasized that the numerical value of latitude by astronomical observing is most fundamental survey framework and traversing corresponds to the detail mapping. The author evaluates his new theories.

Inoh’s maps are divided to “The large-scale map (“Daizu” 1:36000)”, “The medium- scale map (“Chuuzu” 1:216000)” and “The small-scale map (“Shouzu” 1:432000)”. According to Inoh’s mapping process, a draft map (“Shitazu”) is plotted from his survey data for every one day surveyed area at first. Every “Shitazu” is connected each other to one sheet of “Daizu” and the manuscript maps are prepared. He reproduced Inoh’s maps from these manuscript maps by using needle plotting method. Therefore, we can recognize existing of needle plot hole of surveying data on Inoh’s maps prepared by Inoh Tadataka and his group.

The existent Inoh’s maps are divided to complete maps prepared after the complete of his nationwide survey and intermediate maps prepared after every stage of his survey. Furthermore, besides Inoh’s maps prepared by him and his group themselves, various duplicate maps have been prepared until present time. Duplicate maps vary from faithfully copied to transformed. Especially, Japanese Army, Navy and Ministry of Interior copied Inoh’s maps in the early Meiji period. These copied maps were used for preparing the modern Japanese National Maps.

The third Shogun Tokugawa Iemitu dispatched the patrol inspectors all over the country. for the first time in 1633 (the 10th year of Kan’ei). This dispatch was a shared patrol that divided the country into six regions. When the inspectors of each group had competed their duties, they brought back the Kuni-ezu (provincial maps) of each province and submitted them to the shogun. At this time, there was no information about the style and content of the map, so the maps of each province were not uniform in size, drawing style, or contents. Therefore, the shogunate reduced the size of the map to a size that could easily accommodate, the style and content of the map, and created a small-reduced copy of 68 sheets of provincial maps. Incidentally, the author names this secondary manuscript of the 68 provinces’ nationwide maps as “Nippon rokuju-yoshu zu”. This collection of small maps still exists in the family library of several leading daimyo such as Akita, Okayama, and Yamaguchi. The shogunate compiled the national map of Japan (Kan’ei type A) using this small secondary manuscript. This is the first national map of Japan created by the Edo Shogunate.

The author’s research suggests that the first provincial maps of the 68 provinces collected by the patrol inspectors in 1633 were completely destroyed by the Edo Castle fire in 1639. Therefore, it is not possible to know the specific contents of the original temporary Kan’ei 10th year patrol inspector’s map. Thus far, there have been no reported examples of manuscripts or copies of the map of Kan’ei 10th year inspector’s map. However, I was able to confirm the existence of a copy of Suō-Nagato, a pair of provincial maps, which was the Hagi clan submitted to the patrol inspector in 1633.

What was particularly problematic in this study was the fact that Iwakuni Castle had been drawn on the Suō map of the Kan’ei 10th year patrol inspector’s map. Since the dispatch of the patrol inspector was eight years after the Genna “one country, one castle” decree, the illustration of Iwakuni Castle is unnatural. It is generally said that about 400 castles were quickly destroyed by Genna’s decree, However, in realty, it seems that the destruction of each owner’s castle was confusing. In the case of Iwakuni, the destruction of the castle, was not one at a time, and the method of destruction was gradual. The shogunate, which reflected on the Shimabara Rebellion that occurred in 1637, especially requested the countries of western Japan the destruction of the old castle. It was the strong request of the shogunate after the Shimabara Rebellion, that Castle of Iwakuni was destroyed in earnest.

The Iwakuni Castle depicted in the 1633 submission is very different from the one shown in the Keichō provincial map and is a rough depiction reminiscent of an emergency restoration after it was destroyed. The Iwakuni clan’s response to the Kan’ei 10th year patrol inspector was formal and ceremonial, and the full-scale destruction of the castle must be followed the strict demands of the Shogunate after the Shimabara Rebellion. Judging from such a process, the Suō-Nagato provincial map that the Hagi clan submitted to the patrol inspector in 1633 was inadequate. However, Iwakuni Caste was replaced by an old castle in the small secondary manuscript that was later remade by shogunate based on the inspector’s map in 1633 (the Kan’ei 10th year).