The term RTLS was created (circa 1998) at the ID EXPO trade show by Tim Harrington (WhereNet), Jay Werb (PinPoint), and Bert Moore (Automatic Identification Manufacturers, Inc., AIM).
It was created to describe and differentiate an emerging technology that not only provided the automatic identification capabilities of active RFID tags, but also added the ability to view the location on a computer screen.
In the early 1990s, the first commercial RTLS were installed at three healthcare facilities in the United States and were based on the transmission and decoding of infrared light signals from actively transmitting tags.
RTLS reference points, which can be either transmitters or receivers, are spaced throughout a building (or similar area of interest) to provide the desired tag coverage.
Alternately, a choke point identifier can be received by the moving tag and then relayed, usually via a second wireless channel, to a location processor.
The use of directional antennas, or technologies such as infrared or ultrasound that are blocked by room partitions, can support choke points of various geometries.
[2] ID signals from a tag are received by a multiplicity of readers in a sensory network, and a position is estimated using one or more locating algorithms, such as trilateration, multilateration, or triangulation.
Equivalently, ID signals from several RTLS reference points can be received by a tag and relayed back to a location processor.
The newly declared human right of informational self-determination gives the right to prevent one's identity and personal data from being disclosed to others and also covers disclosure of locality, though this does not generally apply to the workplace.
Several prominent labor unions have spoken out against the use of RTLS systems to track workers, calling them "the beginning of Big Brother" and "an invasion of privacy".
However, having distinct signal strength fingerprints in each location typically requires a fairly high saturation of transmitters.
Recognizing a reported location steadily apart from physical presence generally indicates the problem of insufficient over-determination and missing of visibility along at least one link from resident anchors to mobile transponders.
Location of residing objects gets reported moving, as soon as the measures taken are biased by secondary path reflections with increasing weight over time.
This may be defined in specifications for trilateration, triangulation, or any hybrid approaches to trigonometric computing for planar or spherical models of a terrestrial area.
A study carried out by Dr Erik Jan van Lieshout of the Academic Medical Centre of the University of Amsterdam published in JAMA (Journal of the American Medical Equipment)[27] claimed "RFID and UWB could shut down equipment patients rely on" as "RFID caused interference in 34 of the 123 tests they performed".
So placing readers in utility rooms, near elevators and above doors between hospital wings or departments to track assets is not a problem".
[29] However the case of ”keeping at a reasonable distance” might be still an open question for the RTLS technology adopters and providers in medical facilities.
Wrong design decisions made at early stages can lead to catastrophic results for the system and a significant loss of money for fixing and redesign.