Activities on Tides at Hydrographic Department in Meiji Era

Abstract

At the end of 19th century, Japan Hydrographic Department adopted Indian Spring Low Water as the chart datum of Japanese charts. The reason why it was adopted was that the chart datum was able to be determined by the short term tidal observation. It was not examined whether the Indian Spring Low Water is suitable for Japanese chart datum or not, because Japan Hydrographic Department did not have enough knowledge on the tides in those days.