●Introduction

  It is during the Asuka period (7th century) in Japan that orientation became an important factor in designing large-scale structures such as mausoleums and streets as well as capital cities. Three north-south streets were constructed across Nara basin (three red vertical lines in the left image).

  In November 2004, we conducted a GPS survey of the kofun and palaces of the Asuka region using DGPS (Differential GPS), which is capable of providing instant high-precision measurements to an accuracy of 30 centimeters.

   We paid the special attention to the latest group of kofun (burial mounds) built around AD 800. These kofun are positioned along and near what is commonly referred to as the "sacred line/zone," the straight line cutting across, and extending north and south from, the heart of the ancient capital city of Fujiwara-kyo (white vertical line in above two images; hereafter "north-south axis line"). Kofun mounds on the sacred line are believed to be the ones for princes of Tenmu and Gito (they were married), but epitaphs are very rare in Japan, so it is not certain.

   The position of the mausoleum of Emperor Tenji in Yamashina, Kyoto, was also measured by portable GPS by Dr. Uno. It is found that his mausoleum is 50 km north of Fujiyara-kyo, but just on the north-south axis line of Fujiwara-kyo by the error of 40m (see above left image). If this is not a coincidence, it is possible that very accurate base line was drawn when Emperor Tenji built Ohtsu-no-miya, which locate to the north-east of the mausoleum.

   Thumbnail images of the measured sites and latitude & longitude table are here. Bigger images can be found in two .htm files vol 1.and vol 2. Sorry that these pages are Japanese only.

●Sacred line?

   The notion of the sacred line was first proposed by Dr. Toshio Kishi. But there are east-west offsets from the north-south axis line, so sometimes referred to as the sacred zone. Moreover there are some kofun (e.g., Marukoyama and Tsukamyojin kofun) built at the same period but outside the sacred line/zone. So Dr. Kunihiko Kawakami does not accept this notion, and insist that there was a mausoleum area of a few km wide to the south of Fujiwara kyo.

  Our results confirmed that the area's kofun mounds stood slightly off to the east and west of the sacred line, as had already been pointed out. But we found that the north-south distance between kofun mounds and southern (or the northern for Shoubuike kofun) edges of the mausoleum of Temmu&Jito were all integral multiples of 600 shaku, in the unit of measurement called komajaku (one shaku roughly equals 0.352 meters).

  The points of the right image are measured points. We measured 4 to 6 points around kofun mounds in case of off-limits. The points of the previous image are actually the averages of these points. The brown lines are contour lines from the 1/25000 map issued by Geographical Survey Institute, Japan. In this map, south-east (lower right) is high and north-west (upper left) is low, and this map shows that Asuka is somewhat mountainous. If we look the contour line, kofun mounds are located at or near the highest points on the integral multiples of 600 shaku east-west lines.

  So we present one interpretation that directions and lengths are measured accurately at the construction, north-south distance is determined by the integral multiples of 600 shaku from the mausoleum of Temmu&Jito, and sometimes the location is off to the east, depending on the geography.
  We will continue GPS survey of ruins in Japan. In January, 2005, we conducted the GPS measurement of the ruin of Sufukuji temple, which is related to Ohtsu no miya. The results will be presentd soon.

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  　This page is based on the draft titled "GIS and Astronomical Research on the Ancient Capital Cities in Japan" for the presentation in the international symposium "Reading Historical Spatial Information from around the World", held at International Research Center for Japanese Studies, Kyoto, Japan, in February 7-11, 2005.

Three pages below are Japanese.
Thumnail images and data
Larger images Vol.1
Larger images Vol.2

English top page

Related External Links (English)

ASUKA HISTORICAL MUSEUM : introduction to archaeological sites in Asuka
Kitora Kofun by Steve Renshaw and Saori Ihara, on the star chart of Kitora kofun.

2005.2.7. English version 1.0
Copyright(C) 2005, UNO Takao, MIYAHARA Kengo, and USUI Tadashi, All Rights Reserved