Laser rangefinders – precise to a micrometre.
They are often encountered in unexpected places: police "laser speed guns". The officers use them to determine the speed of a car based on the time the laser beam needs to travel from the object back to the origin.
These devices are actually simple laser rangefinders. They are also suitable for measuring rooms, even very narrow spaces. But they are also suitable for measuring or mapping out large, wide areas.
The reference value for measuring speed with the laser gun is the speed of light, as this is the speed at which the laser light travels. Experts call this method "time of flight". Two other measuring methods are the light section method and triangulation.
The latter refers to measuring terrain. By the way: When the police measures the speed of a car with a laser gun, it is usually an absolute measurement.
This works up to a distance of 200 metres between measuring device and target object. A trap that no speed demon can escape.