Z-Axis Test Facility: Improving Indoor Localization for Public Safety

The Z-Axis Test Facility, developed by the National Institute of Standards and Technology (NIST) Public Safety Communications Research (PSCR) Division, is outfitted with a state-of-the-art motion capture system of 50 cameras capable of continuously tracking object movement with sub- centimeter-level accuracy. Located within a multistory test environment tracking ~15m in vertical axis, the facility provides high-frequency data (up to 1000hz object tracking and 240hz full image capturing) that is essential for advancing vertical (Z-axis) positioning technologies. In addition, the tracking capabilities support a multitude of assets simultaneously. This research directly supports public safety communications, where the ability to pinpoint the exact x, y, and z-axis location of a responder can be the difference between life and death.

Multistory, Trusted Test Environment 

The Z-Axis Test Facility has been built out in a four-story stairwell, with a volume of 450 m³, giving researchers the ability to replicate a wide range of vertical navigation challenges faced by first responders.

By adhering to international standards, such as ISO/IEC 18305, the facility ensures that the research conducted and the measurements taken are rigorous, standardized, and comparable with other efforts worldwide. This alignment strengthens the credibility of results while also supporting the global research community in indoor positioning and localization.

Precision Through Motion Capture 

By combining sub-centimeter-level optical tracking with vertical motion scenarios, the Z‑Axis Test Facility provides robust ground-truth data crucial for:

• Evaluating vertical positioning accuracy in multi‑floor tracking systems
• Benchmarking sensor-based localization approaches, including inertial, RF, and vision‑based methods
• Modeling horizontal and vertical error propagation and calibration needs in 3D indoor positioning
• Testing infrastructure-free indoor localization, mapping, and navigation solutions

Impact on Public Safety Communications

Public safety stakeholders have repeatedly identified indoor localization as a key technology gap. While global positioning systems (GPS) have revolutionized outdoor navigation, they are largely ineffective indoors, and especially poor at determining altitude.

By generating high-frequency, ground-truth datasets in a multistory environment, the Z-Axis Test Facility directly addresses this gap and enables developers, industry partners, and public safety organizations to validate and refine technologies that will ultimately allow incident commanders to know precisely where their responders and assets are located within a building.

By producing reliable, sub-centimeter-accurate ground-truth data, this world-class facility enables NIST PSCR to conduct measurements necessary to improve Z-axis positioning technologies and contribute revisions to an international standard, helping bring reliable, life-saving localization capabilities into the hands of first responders.