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Ranging is a process or method to determine the distance from one location or position to another location or position. Another term for this method is lateration. Further development led to cooperative systems, where both locations are equipped with respective apparatus and thus provide bilateral measuring and to multilateral measurement between a larger set of locations, see multilateration.
Members in the class of active ranging systems operate with unilateral transmission and passive reflections, as
- SONAR (= SOund Navigation And Ranging),
- RADAR (= RAdio Detection And Ranging) and
- LIDAR (= LIght Detection And Ranging).
Special ranging makes use of actively synchronized transmission and travel time measurements, hence the time difference between several received signals is used to determine exact distances. This principle is used with SatNav, the Satellite Navigation class of systems. In conjunction with a standardized model of the Globe surface a certain location on the Globe may be determined with high accuracy. Ranging methods without accurate time synchronization of the receiver are called pseudorange, used e.g. in GPS positioning.
With other systems ranging is obtained from passive radiation measurements only, hence the noise or radiation signature of the object is generating the signal that is computed for range. However such asynchronous method requires multiple measurements to obtain range by taking multiple bearings instead of appropriate scaling of active pings, otherwise the system is just capable to provide a simple bearing from any sole measurement.
Ranging is the term merely applying for distance metering with moving objects. Combining several metering results in a time sequence leads to tracking and tracing. Commonly used term for residing terrestrial objects is surveying.