How does RedLore achieve 15cm (1/2 foot) positioning accuracy?

RedLore’s Locus ‘High-Res’ RTLS (on-site positioning) solution provides an accuracy up to 15cm/½ft. This is made possible through RedLore’s unique and patented use of Ultra Wide Band or UWB to determine the distance between the positioning tag attached to the object to be located and reference devices at known locations, called anchors. 

 

UWB uses the time it takes a signal to travel from the anchor to the object to determine the distance. When the signal travels through air, it travels at nearly the speed of light in vacuum: 3 x 108 m/s (meter per second). When travelling through more dense media, such as a person or building materials, it slows down a little bit: 2.25 x 108 m/s when travelling through a person and 2 x 108 m/s through glass. Because the distance travelled through air is usually much bigger than the distance through anything else, we can assume the signal travelled exclusively through air without introducing much error. In addition, from measuring the strength of the received signal, we get a good idea of how much material other than air stand between the object and the anchor, which allows us to adjust the calculated distance and increase the accuracy even further. 

 

Most other RTLS technologies, such as those based on Bluetooth and WIFI, rely only on the difference between the signal strength as sent by the transmitter and the signal strength at the receiver. This difference in signal strength, in other words the weakening or attenuation of the signal, is then used to estimate the distance between the anchor and the object. The problem with this approach is that when a signal travels through a human body or a wall, the weakening of the signal is so large that the distance calculation yields a result that is sometimes 2x or even larger than had there only been air between the anchor and the tag. Large errors such as these make that such RTLS system cannot usually offer any better than 3m/10 ft accuracy, which at some locations worsens to 5m/16ft or more.