Femtometer
A femtometer (fm) is a unit of length in the metric system, equal to one-quadrillionth of a meter (1 fm = 10⁻¹⁵ meters). It is also known as a fermi, named after the physicist Enrico Fermi. Femtometers are used to measure extremely small distances at the subatomic level, such as the size of protons, neutrons, and atomic nuclei. For example, the radius of a proton is about 0.84 femtometers. This unit is commonly used in nuclear physics and particle physics, but it's far too small for everyday measurements.
Link (US Survey)
The US survey link is a unit of length used in the United States for land surveying, defined as exactly 7.92 US survey inches. Since one US survey inch is slightly longer than the international inch (due to the US survey foot), the US survey link is approximately 0.201168 meters.
It is part of the US survey system, derived from Gunter’s chain, which is divided into 100 links per chain (66 US survey feet). Links are used to measure small distances in surveying and land measurement.
Key facts:
1 US survey link = 7.92 US survey inches
1 US survey link ≈ 0.201168 meters
100 links = 1 US survey chain (66 US survey feet)
25 links = 1 US survey rod (16.5 US survey feet)
Though the US survey units are being phased out, the US survey link still appears in historical land records and legal surveying documents.
No conversions available for length.