Indoor navigation technology covers the hardware and signal-processing methods that allow a smartphone, wearable or tag to determine its position inside a building where GPS signals do not reliably reach. Several distinct technologies are used, each with different accuracy characteristics, infrastructure requirements and operational trade-offs. Understanding what each method actually measures, and where it breaks down, is the starting point for any deployment.
Bluetooth Beacon-Based Positioning
Bluetooth Low Energy (BLE) beacons are the most widely used positioning technology for indoor wayfinding in retail, museums and venues. A beacon is a small radio transmitter that broadcasts a packet containing identifiers at a set interval. The receiving device — typically a smartphone running a suitable native application or a dedicated receiver; ordinary browser support is limited and should not be treated as passive beacon scanning — measures the received signal strength indicator (RSSI) from one or more beacons and uses that to infer distance.
There are two main approaches. Proximity zoning places a beacon at a fixed point and triggers a response when the device enters a rough radius around it. This is simple to set up and works well for exhibit information or zone-based notifications, but it does not produce a continuous position on a map. Trilateration uses RSSI readings from three or more beacons to calculate an estimated coordinate. This enables a blue-dot experience on a floor plan, but the maths is sensitive to signal variation.
Practical limitations of RSSI
RSSI is not a clean measure of distance. It fluctuates with the number of people in the space, the orientation of the receiving device, and the presence of metallic fixtures, glass partitions or racking. A beacon mounted on a metal column will produce a very different signal pattern from one mounted on a plasterboard wall at the same height. Because of this, any accuracy claim attached to a beacon system is only valid for the specific environment in which it was measured. A figure quoted for an open-plan office will not transfer to a cluttered warehouse or a stone-walled museum gallery.
Calibration — taking RSSI readings at known distances in the actual venue — improves reliability, but it does not eliminate environmental variation. Beacon density also matters: spacing beacons too far apart leaves gaps in coverage where the device cannot see enough transmitters for trilateration, while placing them too close increases interference and raises the ongoing battery replacement burden.
Wi-Fi-Based Indoor Positioning
Most large venues already have a Wi-Fi access point (AP) network, and that infrastructure can be repurposed for indoor positioning. The two principal methods are fingerprinting and trilateration.
Fingerprinting involves a site survey: an engineer walks through the venue with a device, recording the RSSI from every visible AP at multiple points on the floor plan. The resulting radio map is stored on a server. When a user's device reports which APs it can see and at what signal strengths, the system compares that fingerprint against the map and returns the closest match. This can produce reasonable accuracy in a stable environment, but the radio map degrades whenever APs are moved, repositioned, retuned or replaced — which is a routine occurrence in managed Wi-Fi networks.
Trilateration using Wi-Fi works on the same principle as BLE trilateration but with APs instead of beacons. Wi-Fi signals generally have longer range and pass more readily through some building materials, which can be an advantage in large open spaces. However, APs are typically mounted high on ceilings or walls for coverage rather than for positioning, so their placement is rarely optimised for accurate location. Power levels change automatically in many enterprise Wi-Fi systems, further shifting the signal landscape without warning.
Wi-Fi positioning also raises privacy considerations. The device must actively scan for networks or exchange packets with APs, which means the venue's network can observe device presence. Under UK data protection law, this needs to be assessed carefully, particularly if MAC-address tracking is involved rather than an opt-in app interaction.
UWB for High-Accuracy Indoor Navigation
Ultra-wideband (UWB) operates very differently from BLE and Wi-Fi. Instead of measuring signal strength, UWB measures the time of flight of very short radio pulses between a tag or smartphone and fixed anchors. Because the pulses are extremely brief — nanoseconds wide — the timing resolution is fine enough to calculate distance with centimetre-level precision in controlled conditions.
UWB may suit controlled applications that need fine ranging, such as tracked tools or equipment, after a safety and performance pilot. It should not be treated as a sole safety control or assumed to work on every visitor device. For general visitor wayfinding in a museum or shopping centre, UWB is rarely the right choice because it requires a dense network of powered anchors, and the receiving device must have a UWB radio — which is present in recent smartphones but absent in many older or budget models.
Installation is more involved than dropping beacons onto adhesive mounts. UWB anchors need careful positioning, a clear line of sight to each other and to the tags, and a reliable power or PoE connection. Ceiling height, racking geometry and the presence of metal all affect performance. A pilot in the actual space, with the actual fixtures and stock in place, is essential before committing to a full rollout.
Sensor Fusion Approaches
No single indoor positioning technology works well in every part of a building. Sensor fusion combines inputs from multiple sources — BLE beacons, Wi-Fi, UWB and the device's own inertial measurement unit (IMU) — to produce a more stable and continuous position estimate than any one source could deliver alone.
The IMU in a smartphone includes an accelerometer, a gyroscope and sometimes a magnetometer. By integrating these readings over time, the system can track the device's movement between position fixes from beacons or Wi-Fi. This is known as dead reckoning. It fills in the gaps when radio signals are temporarily blocked — for example, when a visitor walks through a lift lobby or a narrow corridor with no beacons. However, dead reckoning drifts: small errors in each step accumulate, so the position gradually diverges from reality unless a radio fix arrives to correct it.
Fusion systems vary in sophistication. A basic approach might use beacon trilateration when enough beacons are visible and fall back on dead reckoning when they are not. A more advanced system might apply a Kalman filter that continuously weights each input according to its estimated reliability, suppressing sudden jumps when a single beacon produces an anomalous RSSI reading. The complexity of the fusion algorithm affects both the development cost and the processing load on the device or server.
For venues evaluating sensor fusion, the practical question is not whether fusion is better in principle — it usually is — but whether the added implementation complexity and ongoing calibration justify the improvement over a simpler beacon-only or Wi-Fi-only approach for the specific use case.
Choosing Between Positioning Technologies
Selecting the right technology starts with defining what the navigation system actually needs to do, not with comparing specification sheets. The following criteria tend to matter most in practice.
- Accuracy requirement. Does the system need to know which room a visitor is in, which exhibit they are standing beside, or which exact shelf they are reaching for? Room-level accuracy is achievable with basic beacon zoning. Exhibit-level typically needs calibrated trilateration or sensor fusion. Shelf-level usually demands UWB or a very dense beacon grid with careful calibration.
- Device compatibility. If the venue cannot require visitors to install an app, the options narrow. Web-based BLE scanning is possible in some browsers but has significant limitations and inconsistent support across operating systems. Wi-Fi fingerprinting can work without an app but raises privacy questions. UWB requires a UWB-capable device. NFC and QR codes sidestep the device-compatibility problem entirely by putting the interaction in the physical tag rather than the radio system.
- Existing infrastructure. A venue with a recently upgraded enterprise Wi-Fi network may find that Wi-Fi-based positioning adds relatively little marginal hardware cost, even if accuracy is modest. A museum with no Wi-Fi upgrade budget but volunteer labour for beacon mounting may find BLE more practical.
- Maintenance burden. Every battery-powered beacon is a future battery replacement. Every Wi-Fi AP used for positioning is a dependency on the network team's change-management process. Every UWB anchor is a powered device that needs cabling and monitoring. The total cost of ownership over three to five years often favours the simplest system that meets the accuracy requirement.
- Environmental stability. Spaces where fixtures, stock levels or crowd density change frequently — retail floors, event halls — will degrade radio maps and calibration faster than static environments. In unstable environments, simpler zoning approaches that do not depend on a precise radio map are often more robust than fingerprinting.
Questions to put to a supplier
When evaluating a positioning system, the following questions tend to reveal whether a vendor is selling a realistic solution or an idealised demo:
- What accuracy have you measured in a space with similar construction materials and layout, and what method did you use to measure it?
- How does the system behave when a visitor's phone is in a handbag or pocket rather than held in front of them?
- What happens to accuracy when the venue is at peak occupancy compared to empty?
- What calibration is required after installation, and how often must it be repeated?
- How does the system handle devices without the required radio — older phones, budget models, visitors who have disabled Bluetooth?
- What is the ongoing maintenance schedule, and who is responsible for beacon battery replacement, firmware updates and radio-map refreshes?
There is no universally correct choice. The right technology is the one that delivers sufficient accuracy for the use case, works on the devices the audience actually carries, and can be maintained within the venue's operational capacity over the long term. Piloting in a representative section of the real venue, with real visitors, remains the only reliable way to confirm that a chosen approach will perform as expected in day-to-day operation.
