Astronomy and surveying

The Japanese characters for "survey" come from a Chinese expression meaning "Gauge the sky, weight the earth." In the Edo Period, surveying techniques spread as practical skill as Western astronomical and surveying knowledge blended with traditional Japanese surveying techniques. The civil engineering, flood control, and miniing projects that proliferated in the Edo Period were only possible because of the widespread diffusion of surveying techniques.

This astronomical calendar introduced to Japan from China, also included the daily positions of the sun, moon and the fice stars, but ciased to be used by the Muromachi period. In the Edo period, Shibukawa initiated the calendar reform (jyukyo kaireki). This display is one of the early lunar calendar calculated in 1617. This was in print from 1685 until the end of the Edo period.

In the West, the terrestrial globe and astronomical sphere were used equally. In addition to these, the kontengi (astrolabe) imported from Chiana was also used and possessed by scholars of astronomical calendars and rampeki daimyo (Hollandaophile daimyo). The first terrestrial globe and astronomical sphere to in Japan is said have been made by the Tokugawa government astronomer Harumi Shibukawa in 1695 and the actual globes (an important cultural property) are currently owned by the National Museum of Nature and Science. This terrestrial globe, which illustrates the map in Mateo Rich form, is identical to the one made by Harumi Shibukawa.

This is technical book on surveying written by Hironaga Kai of the Hitachi Kasama domain, a disciple of Hasegawa of the Seki school. This book was published before the arrival of Commedore Perry and many Western surveying tools were accurately engineered based on a mathematical theory. Wazan scholars began to research the theory and usage of these tools, thus arriving with the publication of numberous technical books on surveying as this book. This book explained in detail the basic choken method which utilized the existing surveying tools made of wood. It also advised readers in the advertisements at the end of the book to only use the sophisticated Western octants after studying the funamentals.

The kenban compass was the most commonly used surveying instrument during the Edo period. This tool is used by forming similar triangle with the target objects on the kenban compass. The kenban compass could be easily made with wood and enabled the measurement of the height of trees and mountains when used horizontally. Moreover, the relatively easy calculation process of similar triangles allowed this tool to be used until the beginning of the Meiji period. There are recordings that the height of Mr. Fuji was measured using this method.

In order to accomplish his purpose of surveying the whole nation of Japan and to measure the distance of 1 degree latitude, Tadataka Ino needed to make accurate astronomical observations throughout the country. The quadrant was one of the surveying equipments used to measure the position of the stars. It was made with reference to the Reidaigishoushi (1674) under the order of master Shigetomi Hazama. There were two quadrants: the large-size quadrant measuring 6 shaku ( or approximately 180 cm) in radius and the middle-size quadrant measuring 3.8 shaku ( or approximately 115 cm) in radius. The middle-size quadrant was used for the nationwide surveying project.

The ryoteizha (measuring wheel) is a surveying equipment which measures the distance between two points using a wheel mechanis, that indicates the distance traveled by multiplying the driving wheel perimeter by the number of wheel rotations. There were several surveying equipments during Tadataka Ino's time, but the ryoteisha was the most commonly used tool for measuring distances. Judging from the poor condition of the roads and the small size of the dricing wheel, it is doubtful that the measurements were accurate. It is thought that this tool was merely used with the aim to have the surveying conditions recognized those conserned.

Drawing tools used is surveying during the Edo period differed slightly depending on the school and year, but were basically tools shich indicated the direction and distance of a location on a smaller scale drawing. Directions were indicated by angles inscribed on the bundono kane (a combination of a circular protractor and ruler), circular protractor, semicircular protractor and quarter circle protractor. The reduced-size drawings were made using the compass and ruler. Like the hoshibiki and subiki which were used to draw dotted lines, pen type writing tools from the West were already utillized during the Edo period. Circular protractor, quarter-circular protractor (or sextant), semi-circular protractor, hoshibiki, compass, needle.