A positioning system is a system for determining the position of an object in

space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually cons ...

. One of the most well-known and commonly used positioning systems is the

Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...

(GPS). Positioning system technologies exist ranging from worldwide coverage with meter accuracy to workspace coverage with sub-millimeter accuracy.

Coverage

Interplanetary systems

Interplanetary-radio communication systems not only communicate with spacecraft, but they are also used to determine their position.

Radar Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, we ...

can track targets near the Earth, but spacecraft in deep space must have a working

transponder In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight trans ...

on board to echo a radio signal back. Orientation information can be obtained using

star tracker A star tracker is an optical device that measures the positions of stars using photocells or a camera. As the positions of many stars have been measured by astronomers to a high degree of accuracy, a star tracker on a satellite or spacecraft may ...

Global systems

Global navigation satellite system A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows satellite navigation devices to determine their location (longitude, latitude, and altitude/elevation) to high pr ...

s (GNSS) allow specialized radio receivers to determine their 3-D space position, as well as time, with an accuracy of 2–20 metres or tens of nanoseconds. Currently deployed systems use microwave signals that can only be received reliably outdoors and that cover most of Earth's surface, as well as near-Earth space. The existing and planned systems are: *

– US military system, fully operational since 1995 *

GLONASS GLONASS (russian: ГЛОНАСС, label=none, ; rus, links=no, Глобальная навигационная спутниковая система, r=Global'naya Navigatsionnaya Sputnikovaya Sistema, t=Global Navigation Satellite System) is ...

– Russian military system, fully operational since October 2011 * Galileo – European Community, fully operational since December 2019 *

Beidou navigation system The BeiDou Navigation Satellite System (BDS; ) is a Chinese satellite navigation system. It consists of two separate satellite constellations. The first BeiDou system, officially called the BeiDou Satellite Navigation Experimental System and ...

– China, fully operational since June 2020 *

Indian Regional Navigation Satellite System The Indian Regional Navigation Satellite System (IRNSS), with an operational name of NavIC (acronym for 'Navigation with Indian Constellation; also, 'sailor' or 'navigator' in Indian languages), is an autonomous regional satellite navigation s ...

– a planned project in India

Regional systems

Networks of land-based positioning transmitters allow specialized radio receivers to determine their 2-D position on the surface of the Earth. They are generally less accurate than GNSS because their signals are not entirely restricted to line-of-sight propagation, and they have only regional coverage. However, they remain useful for special purposes and as a backup where their signals are more reliably received, including underground and indoors, and receivers can be built that consume very low battery power.

LORAN LORAN, short for long range navigation, was a hyperbolic radio navigation system developed in the United States during World War II. It was similar to the UK's Gee system but operated at lower frequencies in order to provide an improved range u ...

is an example of such a system.

Local systems

A local positioning system (LPS) is a navigation system that provides location information in all weather, anywhere within the coverage of the network, where there is an unobstructed

line of sight The line of sight, also known as visual axis or sightline (also sight line), is an imaginary line between a viewer/observer/ spectator's eye(s) and a subject of interest, or their relative direction. The subject may be any definable object taken ...

to three or more signaling

beacon A beacon is an intentionally conspicuous device designed to attract attention to a specific location. A common example is the lighthouse, which draws attention to a fixed point that can be used to navigate around obstacles or into port. More mode ...

s of which the exact position on Earth is known. Unlike

GPS The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...

or other

global navigation satellite system A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows satellite navigation devices to determine their location (longitude, latitude, and altitude/elevation) to high pr ...

s, ''local positioning systems'' don't provide global coverage. Instead, they use (a set of) beacons, which have a limited range, hence requiring the user to be near these. Beacons include cellular base stations,

Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio wav ...

and LiFi access points, and radio broadcast towers. In the past, long-range LPS's have been used for navigation of ships and aircraft. Examples are the

Decca Navigator System The Decca Navigator System was a hyperbolic radio navigation system which allowed ships and aircraft to determine their position by using radio signals from a dedicated system of static radio transmitters. The system used phase comparison of t ...

and

. Nowadays, local positioning systems are often used as complementary (and in some cases alternative) positioning technology to GPS, especially in areas where GPS does not reach or is weak, for example, inside buildings, or

urban canyon An urban canyon (also known as a street canyon) is a place where the street is flanked by buildings on both sides creating a canyon-like environment, evolved etymologically from the Canyon of Heroes in Manhattan. Such human-built canyons are made ...

s. Local positioning using cellular and broadcast towers can be used on cell phones that do not have a GPS receiver. Even if the phone has a GPS receiver, battery life will be extended if cell tower location accuracy is sufficient. They are also used in trackless amusement rides like

Pooh's Hunny Hunt Pooh's Hunny Hunt is a unique trackless dark ride located at Tokyo Disneyland. It is based on the 1977 Disney animated film '' The Many Adventures of Winnie the Pooh''. History After the rise in popularity of Walt Disney's film adaptation of Wi ...

and Mystic Manor. Examples of existing systems include * Locata Corporation * Pseudolite

Indoor systems

Indoor positioning systems are optimized for use within individual rooms, buildings, or construction sites. They typically offer centimeter-accuracy. Some provide 6-D location and orientation information. Examples of existing systems include * Active Bat

Workspace systems

These are designed to cover only a restricted workspace, typically a few cubic meters, but can offer accuracy in the millimeter-range or better. They typically provide 6-D position and orientation. Example applications include

virtual reality Virtual reality (VR) is a simulated experience that employs pose tracking and 3D near-eye displays to give the user an immersive feel of a virtual world. Applications of virtual reality include entertainment (particularly video games), e ...

environments, alignment tools for

computer-assisted surgery Computer-assisted surgery (CAS) represents a surgical concept and set of methods, that use computer technology for surgical planning, and for guiding or performing surgical interventions. CAS is also known as computer-aided surgery, computer-assist ...

or radiology, and cinematography ( motion capture,

match moving In visual effects, match moving is a technique that allows the insertion of computer graphics into live-action footage with correct position, scale, orientation, and motion relative to the photographed objects in the shot. The term is used loos ...

). Examples:

Wii Remote The Wii Remote, also known colloquially as the Wiimote, is the primary game controller for Nintendo's Wii home video game console. An essential capability of the Wii Remote is its motion sensing capability, which allows the user to interact wi ...

with Sensor Bar, Polhemus Tracker, Precision Motion Tracking Solutions InterSense.

High performance

High performance positioning system is used in manufacturing processes to move an object (tool or part) smoothly and accurately in six degrees of freedom, along a desired path, at a desired orientation, with high

acceleration In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by t ...

, high

deceleration In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by t ...

, high

velocity Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity i ...

and low

settling time In control theory the settling time of a dynamical system such as an amplifier or other output device is the time elapsed from the application of an ideal instantaneous step input to the time at which the amplifier output has entered and remained ...

. It is designed to quickly stop its motion and accurately place the moving object at its desired final position and orientation with minimal jittering. Examples: high velocity

machine tool A machine tool is a machine for handling or machining metal or other rigid materials, usually by cutting, boring, grinding, shearing, or other forms of deformations. Machine tools employ some sort of tool that does the cutting or shaping. All ...

s, laser scanning,

wire bonding Wire bonding is the method of making interconnections between an integrated circuit (IC) or other semiconductor device and its packaging during semiconductor device fabrication. Although less common, wire bonding can be used to connect an IC ...

, Printed circuit board inspection, lab automation assaying,

flight simulator A flight simulator is a device that artificially re-creates aircraft flight and the environment in which it flies, for pilot training, design, or other purposes. It includes replicating the equations that govern how aircraft fly, how they rea ...

Technologies

Multiple technologies exist to determine the position and orientation of an object or person in a room, building or in the world.

Acoustic positioning

Time of flight

Time of flight Time of flight (ToF) is the measurement of the time taken by an object, particle or wave (be it acoustic, electromagnetic, etc.) to travel a distance through a medium. This information can then be used to measure velocity or path length, or as a w ...

systems determine the distance by measuring the time of propagation of pulsed signals between a transmitter and receiver. When distances of at least three locations are known, a fourth position can be determined using

trilateration Trilateration is the use of distances (or "ranges") for determining the unknown position coordinates of a point of interest, often around Earth (geopositioning). When more than three distances are involved, it may be called multilateration, for e ...

is an example. Optical trackers, such as laser ranging trackers suffer from

problems and their performance is adversely affected by ambient light and infrared radiation. On the other hand, they do not suffer from distortion effects in the presence of metals and can have high update rates because of the speed of light. Ultrasonic trackers have a more limited range because of the loss of energy with the distance traveled. Also they are sensitive to ultrasonic ambient noise and have a low update rate. But the main advantage is that they do not need line of sight. Systems using

radio waves Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz ( GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (s ...

such as the

do not suffer ambient light, but still need line of sight.

Spatial scan

A spatial scan system uses (optical) beacons and sensors. Two categories can be distinguished: * Inside out systems where the beacon is placed at a fixed position in the environment and the sensor is on the object * Outside in systems where the beacons are on the target and the sensors are at a fixed position in the environment By aiming the sensor at the beacon the angle between them can be measured. With triangulation the position of the object can be determined.

Inertial sensing

The main advantage of an inertial sensing is that it does not require an external reference. Instead it measures rotation with a gyroscope or position with an

accelerometer An accelerometer is a tool that measures proper acceleration. Proper acceleration is the acceleration (the rate of change of velocity) of a body in its own instantaneous rest frame; this is different from coordinate acceleration, which is acc ...

with respect to a known starting position and orientation. Because these systems measure relative positions instead of absolute positions they can suffer from accumulated errors and therefore are subject to drift. A periodic re-calibration of the system will provide more accuracy.

Mechanical linkage

This type of tracking system uses mechanical linkages between the reference and the target. Two types of linkages have been used. One is an assembly of mechanical parts that can each rotate, providing the user with multiple rotation capabilities. The orientation of the linkages is computed from the various linkage angles measured with incremental encoders or potentiometers. Other types of mechanical linkages are wires that are rolled in coils. A spring system ensures that the wires are tensed in order to measure the distance accurately. The degrees of freedom sensed by mechanical linkage trackers are dependent upon the constitution of the tracker's mechanical structure. While six degrees of freedom are most often provided, typically only a limited range of motions is possible because of the kinematics of the joints and the length of each link. Also, the weight and the deformation of the structure increase with the distance of the target from the reference and impose a limit on the working volume.A SURVEY OF TRACKING TECHNOLOGY FOR VIRTUAL ENVIRONMENTS, Jannick P. Rolland, Yohan Baillot, and Alexei A. Goon, Center for Research and Education in Optics and Lasers (CREOL), University of Central Florida, Orlando FL 32816

Phase difference

Phase difference In physics and mathematics, the phase of a periodic function F of some real variable t (such as time) is an angle-like quantity representing the fraction of the cycle covered up to t. It is denoted \phi(t) and expressed in such a scale that it v ...

systems measure the shift in phase of an incoming signal from an emitter on a moving target compared to the phase of an incoming signal from a reference emitter. With this the relative motion of the emitter with respect to the receiver can be calculated. Like inertial sensing systems, phase-difference systems can suffer from accumulated errors and therefore are subject to drift, but because the phase can be measured continuously they are able to generate high data rates. Omega (navigation system) is an example.

Direct field sensing

Direct field sensing systems use a known field to derive orientation or position: A simple

compass A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose, which can pivot to align itself wit ...

uses the

Earth's magnetic field Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic ...

to know its orientation in two directions. An inclinometer uses the earth gravitational field to know its orientation in the remaining third direction. The field used for positioning does not need to originate from nature, however. A system of three electromagnets placed perpendicular to each other can define a spatial reference. On the receiver, three sensors measure the components of the field's flux received as a consequence of

magnetic coupling A magnetic coupling is a coupling that transfers torque from one shaft to another, but using a magnetic field rather than a physical mechanical connection. Magnetic shaft couplings are most often used for liquid pumps and propeller systems, since ...

. Based on these measures, the system determines the position and orientation of the receiver with respect to the emitters' reference.

Optical systems

Optical positioning systems are based on

optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultrav ...

components, such as in total stations.

Magnetic positioning

Hybrid systems

Because every technology has its pros and cons, most systems use more than one technology. A system based on relative position changes like the inertial system needs periodic calibration against a system with absolute position measurement. Systems combining two or more technologies are called hybrid positioning systems. Hybrid positioning systems are systems for finding the location of a mobile device using several different positioning technologies. Usually GPS (

) is one major component of such systems, combined with cell tower signals, wireless internet signals,

Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limi ...

sensors,

IP address An Internet Protocol address (IP address) is a numerical label such as that is connected to a computer network that uses the Internet Protocol for communication.. Updated by . An IP address serves two main functions: network interface ident ...

es and network environment data. These systems are specifically designed to overcome the limitations of GPS, which is very exact in open areas, but works poorly indoors or between tall buildings (the

effect). By comparison, cell tower signals are not hindered by buildings or bad weather, but usually provide less precise positioning. Wi-Fi positioning systems may give very exact positioning, in urban areas with high Wi-Fi density - and depend on a comprehensive database of Wi-Fi access points. Hybrid positioning systems are increasingly being explored for certain civilian and commercial

location-based service A location-based service (LBS) is a general term denoting software services which use geographic data and information to provide services or information to users. LBS can be used in a variety of contexts, such as health, indoor object search, en ...

s and location-based media, which need to work well in urban areas in order to be commercially and practically viable. Early works in this area include the Place Lab project, which started in 2003 and went inactive in 2006. Later methods let smartphones combine the accuracy of GPS with the low power consumption of cell-ID transition point finding.Energy-Efficient Positioning for Smartphones using Cell-ID Sequence Matching
by Jeongyeup Paek, Kyu-Han Kim, Jatinder P. Singh, Ramesh Govindan