Indoor location: RTLS, asset tracking, beacons and ultra-wideband
GPS made it ordinary to see where you are, where you are going and everything in between. A real-time location system (RTLS) does the same for the things and people inside a facility: assets, tools, containers, work in progress on a production line, patients, staff. For a long time such systems were rare and costly. Bluetooth Low Energy changed that.
What makes a system real-time
An RTLS knows where an item is, and where it has been, because the item’s tag and the system communicate continuously. The tag has a unique identifier and can carry more: the last and current location, who is using the item, its origin, its maintenance record, its physical condition. Sensors built into the tag supply some of this. The user sees every tagged item and person on a map of the site, which serves warehouse management, production planning and scheduling, and delivery planning.
All real-time location systems track assets, but not every asset-tracking system is an RTLS. The test is continuous communication. A system that records an asset only at fixed points, such as doorways, is not real-time, and neither is one built on passive RFID. Such a system cannot show where everything is right now, and it cannot give the history of an item’s path through the building.
The technologies
An RTLS can be built on several technologies. The original comparison ranked them by cost:
- Active RFID. Battery-powered tags transmit to a reader. Indoors. The most expensive group.
- Passive RFID. Transmitters energize the tags, and sectored antennas locate them. Indoors. Also in the most expensive group.
- Wi-Fi. Uses Wi-Fi access points together with GPS. Indoors and outdoors. Mid-priced.
- GPS. Uses satellites. Outdoors. Among the cheapest.
- Bluetooth LE. Uses beacon tags with gateways or phones. Indoors and outdoors. Among the cheapest.
RFID, Wi-Fi and Zigbee need infrastructure whose cost kept many companies from installing an RTLS at all. Bluetooth LE lowered that barrier for three reasons:
- Its hardware is cheap. Beacons are battery-powered transmitters, easy to move when a site changes, and configured from a mobile app.
- Phones can act as the receivers in place of gateways. Almost every phone on the market can read a beacon.
- A beacon network does two jobs at once: it tracks assets in real time, and it collects readings from sensors for motion, light, temperature, humidity and barometric pressure.
What an RTLS is used for
- Asset management. Tracking an asset and how it is used.
- Compliance. Recording who enters a restricted area, and showing that a required procedure was followed, by linking employees to the assets they handle.
- Workforce management. Attendance, process compliance and efficiency monitoring.
- Supply chain. Monitoring raw materials, inventory, parts and products, and tracking shipments, containers and vehicles as they move.
- Safety and security. Knowing where every employee is when someone enters a hazardous area, or during an evacuation.
- Sensing. Monitoring the conditions around an asset, such as humidity, temperature and pressure.
Beacons or ultra-wideband
Both can locate people and assets indoors. They differ in precision, in what each person has to carry, and in what has to be installed.
Beacons broadcast a signal that a phone detects. Software estimates the distance from the signal’s strength, and with three or more beacons it works out a position by trilateration, at best to within a metre. The calculation runs in real time. Beacons cost far less than RFID or Wi-Fi, though the first setup takes care: the transmission power of each beacon may need adjusting until the zones on the floor match the zones in the software. Anyone with a phone can be reached. Nobody needs extra hardware.
Ultra-wideband (UWB) needs anchor antennas in the corners of the space. Each person or asset carries a small battery-powered tag, which signals the anchors, and the anchors calculate its position to within 20 centimetres. Installation and maintenance are simpler than tuning a field of beacons. The limit is the tag: UWB locates only what carries one.
That difference decides most cases:
- Retail. A store wants to show a message when a shopper comes within range of a display. That does not need centimetre precision, and a store cannot hand a tag to every customer. The customer’s own phone is the channel, so beacons fit. UWB could still serve for heat maps, with tags on carts and baskets.
- Museum audio guides. Where visitors download a guide to their own phones, beacons are the better choice. Where the museum hands each visitor an audio device, a UWB tag can go with it, and UWB copes better with crowded exhibits, because there is no beacon power to tune.
- Asset and people tracking. Both work. UWB is more accurate within one room. A building with many rooms is cheaper to cover with a beacon in each than with anchors in the four corners of every room.
In short: UWB is more precise; beacons are cheaper and more adaptable.
Start small
Putting in an RTLS is easier once a vendor and a service provider are chosen. Begin with one small area of the business, and extend it from there.
Adapted in October 2026 from three articles first published on the Momentaj blog in 2017 and 2018. It describes the technology as it stood then.