Convert from fod to gnat's eye

Unit Definition (fod)
The fod is the traditional Danish foot, equal to about 12.365 inches or 31.41 centimeters.

Unit Definition (gnat's eye)
The gnat's eye is an idiomatic "unit" of distance; it's common to hear that something is "as small as a gnat's eye". In fact, the eyes of typical gnats tend to have diameters similar in size to a hair's breadth: roughly 100-150 micrometers (0.10-0.15 millimeters).