Japan longitude and latitude origin

It is the "Japan longitude and latitude origin", which is the reference point for surveying in Japan. A granite monument with a Geospatial Information Authority sign and a metal stud of origin. The longitude and latitude of the whole country are determined based on the values here. "139°44′28".8869 E 35°39′29".1572". In Meiji 7, a naval observation observatory was built here, and in Meiji 21, the same facility, which became the Tokyo Astronomical Observatory, observed stars and determined precise latitude and longitude. After that, triangulation points are determined, and triangular nets are formed throughout the country. The Tokyo Astronomical Observatory was severely damaged by the Great Kanto Earthquake, so it was relocated to Mitaka. It is now the National Astronomical Observatory of Japan.