Active methods use unilateral transmission and passive reflection. Active rangefinding methods include laser, lidar, radar, sonar and ultrasonic rangefinding.
Other devices measure distance using trigonometry are stadiametric, coincidence and stereoscopic rangefinders. Older methodologies that use a couple of known information (usually distance or target sizes) to help make the measurement, have been around in regular use because the 18th century.
Special ranging makes make use of actively synchronized transmission and travel time measurements. Enough time difference between several received signals is employed to determine actual distances (upon multiplication by the speed of light). This principle can be used in satellite navigation. Together with a standardized style of the Earth’s surface, a spot on that surface could be determined with high accuracy. Ranging methods without accurate time synchronization of the receiver are called pseudorange, used, for instance, in GPS positioning.
With other systems ranging is obtained from passive radiation measurements only: the noise or radiation signature of the thing generates the signal that can be used to determine range. This asynchronous method requires multiple measurements to secure a range by firmly taking multiple bearings rather than appropriate scaling of active pings, otherwise the machine is merely with the capacity of providing a straightforward bearing from any single measurement.
Ranging may be the term put on distance measurement with moving objects. Combining several measurements in a period sequence brings about tracking and tracing. A commonly used term for residing terrestrial objects is surveying.