[1] Early Mesopotamian and Egyptian metrologists created a set of measurement standards based on body parts known as anthropic units.
Later agricultural measures such as feet, yards, paces, cubits, fathoms, rods, cords, perch, stadia, miles and degrees of the Earth's circumference, many of which are still in use.
Optical comparators are used when physically touching the part is undesirable; components that consist of fragile or mailable materials require measurement using non-contact techniques.
[5] Measurements are often expressed as a size relative to a theoretically perfect part that has its geometry defined in a print or computer model.
Industrial metrology is common in manufacturing quality control systems to help identify errors in component production and ensure proper performance.