Active Bat is a low-power, wireless

Wireless

Wireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few meters for television remote control, or as far as thousands or even millions of kilometers for deep-space radio communications...

 indoor location

Acoustic location

Acoustic location is the science of using sound to determine the distance and direction of something. Location can be done actively or passively, and can take place in gases , liquids , and in solids .* Active acoustic location involves the creation of sound in order to produce an echo, which is...

 system accurate up to 3 cm

Centimetre

A centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of . Hence a centimetre can be written as or — meaning or respectively...

. It is based on a principle of trilateration

Trilateration

In geometry, trilateration is the process of determinating absolute or relative locations of points by measurement of distances, using the geometry of circles, spheres or triangles. In addition to its interest as a geometric problem, trilateration does have practical applications in surveying and...

, and relies on multiple ultrasonic

Ultrasound

Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...

receivers embedded in the ceiling and measures time-of-flight to them.

Active Bat is an indoor localization system which gives an accuracy in centimeters. This is a range based technique, which works by finding the distance to minimum of three reference nodes and then using multilateration technique to find the exact position. The distance to reference nodes is find out using the time of arrival of infrared signals from the reference nodes.

External links

• The Bat System at Cambridge Computer Laboratory Digital Technology Group