Feet, nautical miles, statutory miles, and meters are all part of the United States Customary Units. "Imperial units" is ambiguous and can refer to many differ

Feet, nautical miles, statutory miles, and meters are all part of the United States Customary Units. "Imperial units" is ambiguous and can refer to many different sets of units all sharing the same name. US Customary units use SI as a baseline for measuring based on physical constants, and standardized conversions from them to units very similar to what was conventional. Eg, since the meter is defined by the distance light travels in a vacuum for the duration of 1/299,792,458 second, and the US defines an inch to be exactly 2.54 cm, any refinement to the speed of light inherently changes the length of an inch. 12 inches equals a foot, a mile equals 5280 feet (exactly 1609.344 meters), and all these things are based on physical constants. Nautical miles are defined as exactly 1852 meters, which is approximately 1.15 miles.