Real-time locating system (RTLS) also known as real-time tracking system is the determination of the location of an identified object at an initially unknown location without further determination of the associated orientation. This makes it possible to determine the location and whereabouts of objects, vehicles or people and link them to their identity.
Positioning requires a well-defined terrestrial coordinate system for the outdoor objects or people – e.g. geographic coordinates or the GPS satellites. The positions to be located can be fixed or in motion. Localization is generally continuous, with a small time interval between the change of location of a moving object and the comparison of its position with fixed objects (the reference points). Since the location determination follows the moving object quickly, it can almost be seen as a measurement of the movement.
Real-time positioning also exists in astronomy, for example in the rapid localization of gamma-ray bursts in order to automatically point other telescopes at this celestial position, or in determining the orbit of very near-Earth asteroids.
Real-Time Systems (Outdoor)
If the task does not only consist of an off-line query, i.e. a search query that is not tied to response times, but rather an online search query with the expectation of a response within a short processing time (dead time, response time), the task is the class of real-time localization and the appropriate support systems are real-time localization systems. These are defined in international standards. RTLS is a combination of special radio components with software suitable for real-time use, with the help of which the locations of objects, vehicles or people are continuously determined by means of a repeatedly repeated time-of-flight measurement. Individual versions of such systems are also standardized.
Technically, the use of a satellite positioning device (e.g. GPS) in conjunction with a mobile phone (GSM) is also a method of real-time localization. Due to a decision of the standards committee, the standardization of the GPS system was deleted from the planning of this committee without further reference to the source. Thus, this combination (GPS with GSM) is not formally an RTLS procedure according to the ISO standards.
Cell Phone Tracking
Technically, logging in a mobile phone to a base station is used to determine the location. By detecting direction and distance, a location in polar coordinates relative to the base station can be determined by such GSM positioning. The resolution of the evaluation depends on the quality of the measuring equipment. As a rule, even when an urban area is densely populated with base stations, no better resolution is possible than with errors of ±30m. In rural areas, the resolution is even coarser.
Discussion on Consent
Generally it collides with the use and acceptance of positioning systems. Every RTLS procedure is always tied to a fixed device and to the voluntary carrying of an RTLS system. However, in the case of real-time localization system use, the subscriber must expressly and individually give his/her consent in order to ensure the legality of the application. Therefore, the explicit consent of the parties involved is mandatory for the legal use of technical solutions.
In some publications, RTLS is equated with RFID, which is technically not true. However, radiofrequency identification (RFID) functions are a subset of real-time localization (RTLS) functions. In some advertising statements, there is no clear distinction between systems for RTLS and solutions with RFID. Any RFID method with characteristics of a location determination is always tied to a stationary device and to the voluntary taking of an RFID system with you.
It is possible to locate objects and infer from the location of the objects to the place where their carrier or user is located. This applies, for example, to mobile phones. The method is called GSM tracking or cell network tracking. This is not an RTLS procedure according to the ISO standards.
Real-Time Indoor Localization
Since reliable GPS positioning is not possible indoors, other technologies are used for this purpose. The most common positioning technologies for indoor positioning include Bluetooth Low Energy (BLE) beacons, Wi-Fi, and ultra-wideband (UWB). With these technologies, in contrast to positioning with GPS, it is also possible to determine the current floor within a building.
On the basis of indoor positioning, various applications can be realized. Indoor navigation, which is mainly used in large buildings such as airports, train stations, shopping malls and campuses, is particularly well-known. Tracking assets and people is also possible and is increasingly being used by companies.