Convert from gnat's eye to foot [survey]

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).

Unit Definition (foot [survey])
A foot (plural: feet) is a non-SI unit of distance or length, measuring around a third of a metre. There are twelve inches in one foot and three feet in one yard.