Kenban compass

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.