These machines measure points on the surface of an object. You can think of it as a digital pitchometer that measures X-Y-Z instead of R-Angle-Drop. These are diameter limited, because the propeller must fit inside the machine’s envelope.
These machines can measure points or scan blade surfaces using an articulated arm to move the measurement head. These are diameter limited due to the arm’s physical extension.
These devices are often handheld and scan blade surfaces using multiple light and laser sensors. The systems are very accurate, portable, and have fewer limitations for size and diameter.