Convert from X unit to arpent [France]

Unit Definition (X unit)
The X-unit (symbol xu) is a unit of length formerly used to measure the wavelength of X-rays and gamma rays. The X-unit is approximately 1.0021×10-13 metre. Defined by the Swedish physicist Karl Manne Georg Siegbahn (1886-1978) in 1925, the X-unit could not at that time be measured directly; the definition was instead made in terms of the spacing between planes of the calcite crystals used in the measuring apparatus.

Unit Definition (arpent [France])
The Arpent is a traditional unit of distance in French-speaking nations. It was used as a land measurement, which is the reason for 'Arpentage' becomming the French word for surveying. It has an official definition of 191.835 English feet (58.471308 meters).