Analysis of information sources in references of the Wikipedia article "List of unusual units of measurement" in English language version.
The land is not let by the acre, but by what is termed a "cow's grass" — so many "cows' grass" to a farm. A "cow's grass" is a measure of land; usually it means as much mountain grazing-land as will keep a cow during the summer, and as much arable-land as will keep the cow-house in fodder during the winter.
Measurements are in metric feet (30cm)...
Maps, architecture and prop models use a scale of 1 foot = 16 units.