Tokyo bearing

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Building with the reference mark in Tokyo

The Nihon Suijun Genten ( Japanese 日本 水準 原点 , German: "Japanese water height reference point") is installed in a small building in the green area in front of the parliament building in Tokyo . It serves as a fixed point for the Japanese reference surface for heights above sea level , which in Japanese is called Tōkyō-wan heikin kaimen ( 東京湾 平均 海面 , "mean sea level [= mean water ] of the Bay of Tokyo ") or as Tokyo Peil ( in short TP, " level Tokyo"), where the word Peilcomes from Dutch. Exceptions are islands apart from the four main Japanese islands.

history

Decided in 1890 and completed in May 1891, the building stood on the site of the then surveying department of the General Staff of the Army with a mark that was 24.5 m above sea level. At that time it was assumed that at this altitude and a foundation that extends to a depth of 10 m, no subsidence would take place. However, a new measurement after the Great Kantō earthquake in 1923 showed a slightly lower value, namely 24.4140 m. A survey after the Tōhoku earthquake in 2011 showed a further lowering to 24.3900 m, plus a shift of the point of 0.0110 seconds in an easterly direction.

Since it is difficult to refer to the height in Tokyo for more distant islands, 37 islands have their own zero point. The heights of Okinawa z. B. are measured from the mean water level of Nakagusuku Bay ( 中 城 湾 , Nakagususku-wan ) and that of Miyake from Ako Bay.

The building ( 日本 水準 原点 標 庫 , Nihon suijun genten-hyō ko ) with the reference mark today has the address 1-1-2 Nagata-chō , Chiyoda-ku , Tōkyō-to . This is the grounds of the Kensei Kinenkan ("Memorial Hall for Constitutional Politics") of the Japanese Parliament . The brand is located inside the building, on the back of the chrysanthemum coat of arms visible from the outside. To mark the centenary of the reference stamp, the Japanese Post issued a stamp on May 30, 1991 with a value of 62 yen and a circulation of 16 million. The leveling device that was used in the Meiji and Taishō periods was obtained from the Berlin company Carl Bamberg . It is now kept in the National Museum of Natural Sciences , Tokyo.

Individual evidence

  1. ↑ 国土 地理 院 時報 . No.100, 2003, 1.1.5 離島 の 高 さ , p. 6 ( PDF ).
  2. ↑ ２ 万 ５ 千 分 １ 地形 図 の 読 み 方 ・ 使 い 方 . Kokudo Chiriin , archived from the original on July 24, 2012 ; Retrieved September 9, 2016 (Japanese).

literature

  • Tokyo-to rekishi kyoiku kenkyu-kai (ed.): Tokyo-to no rekishi sampo (jo). Yamakawa, 2001. ISBN 4-634-29130-4 .

Coordinates: 35 ° 40 ′ 38.1 ″  N , 139 ° 44 ′ 52.3 ″  E