- Japanese: 地高 (jidaka)
Jidaka was a measure of the amount of land, in tan (roughly equiv. to km2), under cultivation in a given domain or other geographical area. While kokudaka was the more standard mode of measure, especially in terms of the Tokugawa shogunate's official ranking and consideration of a domain's wealth, some domains, such as Tosa han, maintained internal accounts in the form of jidaka surveys instead.
Jidaka bears comparison to kokudaka, the amount of rice produced (or equivalent agricultural production) in the domain, as both reflect the overall agricultural strength or ranking of the domain. However, the two are importantly different. Jidaka can indicate an increase in the amount of land under cultivation, but would not capture the increase in production from improved techniques, such as advances in the use of fertilizer, or methods of double-cropping; kokudaka, by contrast, would capture the increase in production, but would not indicate whether such an increase was from improved techniques or from bringing more land under cultivation.
- Luke Roberts, Mercantilism in a Japanese Domain: The Merchant Origins of Economic Nationalism in 18th-Century Tosa, Cambridge University Press (1998), 65-66.