What is the tracking range?
The range indoors with a single set of anchors is up to 100 m × 100 m. The range outdoors can reach up to 200 m × 200 m. If greater coverage is required, multiple systems can be linked together in a mesh network to cover almost unlimited range. Note: The tiny antenna included on the development kit tag was chosen so that the tag can be made as small as possible. It may not have as good a range as other antennas. In a real application, an appropriate antenna would be chosen to give you the best results. The antenna is not required to be mounted on the same pcb as the tag processor. It can be a wearable and external to the tag processor.
What is the power consumption for each tag?
Power consumption depends on the tag update frequency. Typically this will average from 70 mA to 130 mA with update frequencies ranging from 60 Hz to 150 Hz. Power consumption can drop dramatically if the update frequency can be slowed down. For example a 1 Hz update rate will drop the average to 0.26 mA and based on a 500 mAh battery, you can get 400 hours of operation.
What RF frequency does the system operate on?
The RF frequency is Ultra-wideband (UWB) in the range of 3 to 10 GHz. The output level is -41.6 dBm or less, as mandated by the FCC.
What is the update rate for each tag being tracked?
The update rate can be as high as 150 Hz for one tag, but for the development kit with high speed network, it will be up to 100 Hz (10 ms) for each of the four tags. If fewer than 4 tags are used then the update rate will increase up to a max of 150 Hz. As more tags are added beyond four, the latency will increase 2 ms per tag. For example, if you had eight tags, then the latency would be 10 ms + (4 × 2 ms) = 18 ms per tag. This is a 55.5 Hz update rate. To save battery power, the developer can also choose to slow down the update rate. Many applications don’t require high refresh rates.
We also offer the super speed network firmware that will give 100 Hz (10 ms) minimum for 8 tags and 8 anchors.
Is there a limit to the number of tags / users?
There is no hard limit to the number of tags being tracked although our current high speed firmware supports up to 16 tags and 8 anchors. As tag numbers increase the update rate decreases. See the question “What is the update rate for each tag being tracked?” for the formula to calculate the update rate.
How do the anchors know their positions?
When the system is turned on, each anchor runs an algorithm to determine its own position relative to the other anchors.
How long does it take for the anchors to determine their position?
Their positions are determined in less than a second.
What is the tracking precision of each tag?
It is under 5 mm when the tag has a direct line-of-sight to the anchors. Note: The tiny antenna included on the development kit tag was chosen so that the tag can be made as small as possible. It may not have as a good a range as other antennas. In a real application, an appropriate antenna would be chosen to give you the best results. The antenna is not required to be mounted on the same pcb as the tag processor. It can be a wearable and external to the tag processor.
What is the tracking accuracy of each tag?
Accuracy depends on the application and conditions, but typically is within 10 cm. Both anchor and tag locations can be calibrated to remove the offset and achieve better accuracy, but for most applications calibration is not necessary. Here is a document showing typical precision vs accuracy data: Precision vs Accuracy
What is the precision of the 3D rotation quaternion?
The quaternion precision is 0.06 degrees.
What is the accuracy of the 3D rotation quaternion?
The quaternion accuracy depends on the application and conditions, but typically is within 2 degrees on startup. In our virtual reality demo application, we have the user face forward when the demo starts. This calibrates the quaternion and then maintains the 0.06 degree precision.
I’m confused. What is the difference between precision and accuracy?
Accuracy is a measure of closeness to a known value. Precision is a measure of reproducibility. For example, in a dart game with 5mm of precision, the dart would typically hit within 5mm of the other darts, but may or may not be hitting the bullseye.