What is RTLS
A real-time location system (RTLS) reports where tagged people, vehicles, tools, or materials are while they still move. It is a live zone or coordinate, not the last barcode or the last WMS bin.
What RTLS means on the floor
On site, RTLS is a system that reports where tagged people, vehicles, tools, or materials are while they still move. Not the bin someone typed at putaway. Not the station a scanner last saw. A live zone or a live coordinate, updating often enough that a supervisor can send a driver to the right bay instead of starting a hunt. Plants use it for asset tracking that has to stay true during the shift, not only at the next checkpoint.
It is also not GPS for indoors. Satellite signals drop under steel roofs and dense racking. Indoor RTLS uses radios, gate readers, or sensors on the vehicle itself to place the asset on a hall map people already know. That indoor layer is what vendors often call an indoor positioning system. RTLS is the plant name for the same job when the output has to drive a live decision, not a one-off survey.
What last-scan systems do not tell you
Most floors already record location in pieces. A barcode at the dock says the pallet entered. A WMS putaway writes a bin. A MES complete says the job left Station 4. An ERP transfer says the stock moved to a storage location. Those are events. They are true at the moment someone scanned or confirmed. They go stale the second a forklift takes a detour, parks in a buffer, or drops the cage one aisle over because the assigned face was blocked.
That is why empty walks survive in plants that already own warehouse software. Automotive and white-goods halls still lose minutes on “where is the tugger” even when every pallet has an ID, because the ID is not a live location. WIP cages drift. Returnable stillages sit behind a line that is not theirs. A driver radioed “on the way” can be waiting at a shared aisle. RTLS does not replace those systems. It fills the minutes between their events so the map matches the hall.
Tags, anchors, and a live map
A working RTLS has three parts the floor can point at. Tags or beacons announce who they are. Fixed anchors, locators, gateways, or readers sit at known spots in the hall. A location engine turns that radio picture into a position, then a map puts the pin where operators already look: north buffer, dock 2, Line 3 inbound. On BLE, either side can move. Fixed gateways can track beacons on assets, or battery beacons can sit still while a gateway on the forklift calculates its own place. Without the map, you have a table of coordinates. With the map, a supervisor sees the same hall the driver is standing in.
The radio is not one product. Bluetooth Low Energy (BLE) is the usual medium-precision choice at about one to three meters (3 to 10 ft). It installs two ways. Fixed BLE gateways on PoE track movable beacons on assets. Or battery BLE beacons act as static anchors while a BLE gateway on the asset, usually an Android device or a specialized gateway, calculates its own position. The second layout skips hall cabling and fits powered vehicles such as forklifts and AGVs. The first fits tagging many cages or tools that have no onboard power. Coarse zone presence is a different job: you only need to know the asset is in a wing of the building (on the order of 2,000 m² / about 21,500 ft²) or that it passed a chokepoint. That low-accuracy setup is not the same as a 1–3 m (3–10 ft) medium-precision grid. Ultra-wideband (UWB) is the tighter location. RFID is three builds, at different vendors and price points. A gate answers presence at a dock door: the tagged load passed this checkpoint. Proximity says which reader or station heard the tag. The most advanced build is RFID RTLS: antennas on the ceiling that track a live X, Y, and Z, often at about one meter (~3 ft). The split is in RFID for RTLS. Some trucks carry their own localization with SLAM, so the vehicle maps itself against the layout instead of depending on a dense ceiling grid. Wi-Fi can fill a large zone when the plant already has access points and does not need a tight location. Yards still use GPS because the sky is open. The mix is normal. One hall can run gateway-on-truck BLE for the fleet, a gate or proximity RFID read on shipping doors, ceiling-antenna RFID RTLS with a live X, Y, Z on cages that already carry RFID tags, and UWB only on the no-go zone.
What the plant does with the pin is the second half of the system. A live position can stop a search, feed a no-go rule, rebuild a spaghetti path, or show dwell in a blocked buffer. None of that happens if the team only stores coordinates in a historian nobody opens during the shift.
Location accuracy is the decision that matters
Accuracy is not a brochure number you maximize. It is how wrong the location can be before the next action fails. Coarse zone presence only needs to know the asset is in this wing of the building or that it passed a chokepoint. Medium-precision search needs the aisle or buffer: a one-to-three-meter (3–10 ft) BLE reading is enough to kill a five-minute walk, and for most plant logistics jobs that band is already precise. The last meters (last few yards) are still covered on foot. That BLE band holds for both layouts: fixed PoE gateways tracking movable beacons, and battery beacons heard by a gateway on a powered forklift or AGV. Safety lockouts and dock-face confirmation need a tighter floor. Sub-meter (~3 ft) UWB starts to matter when “near the line” is not the same as exact floor position on the mark. Many no-go zones already work at medium precision. A gate RFID read at a dock door is the presence job: the tagged load passed this checkpoint. Proximity RFID names the reader that heard it. Ceiling-antenna RFID RTLS draws the path as a live X, Y, and Z. Those ceiling installs often hold about one meter (~3 ft), in the same band as typical medium-precision BLE, when the plant wants a continuous location and already prefers RFID tags.
Indoor GPS is the trap in a lot of first meetings. It works in the yard. Under a metal roof it does not. Buying a tighter radio than the decision needs also has a cost: more anchors, shorter tag batteries, denser calibration. The companion pages on this wiki walk that split in more detail, from start with the decision, not the technology to compare RTLS technologies.
Metal racking, moving forklifts, and concrete walls bounce radio. A vendor who quotes centimeter (inch) accuracy from an empty lab is not quoting your Hall B. Treat the ranges as what a maintained industrial install usually holds, then walk a short aisle on your floor before you grow the grid.
How plant teams choose a system
1. Name the question this quarter will enforce - If the fight is “which aisle holds the last pallet of that SKU,” medium-precision BLE is the honest start. If you only need “is it still in this wing of the building,” coarse zone presence or a chokepoint read is enough. If the fight is exact floor position on a mark, that geometry itself sets the radio. Do not buy UWB for a search problem, and do not ask BLE to certify a centimetre-scale (inch-scale) floor mark. Many no-go zones already work at medium precision.
2. Separate presence from path - Dock confirmation, shipping-door control, and cage hand-off often need checkpoint RFID or a reader at a known point. Continuous forklift paths, empty-round analysis, and live search need a stream that updates while the vehicle moves. That stream can be BLE, UWB, SLAM, or ceiling-antenna RFID RTLS that reports a live X, Y, and Z, often at about one meter (~3 ft), when the plant already runs RFID tags and wants a live position. A gate or a proximity read is a different RFID price point and does not draw that path. Mixing a presence job into a path SKU, or the other way around, is how plants overpay for gates they could have scanned, or under-instrument halls they expected to map.
3. Put the pin on a hall people already trust - Coordinates in a table still force a translation step. The operational picture that logistics and production will actually use is a live digital twin, the same layer described under types of digital twins. If the map does not match the columns and doors on the floor, the RTLS project becomes another screen nobody opens.
4. Own the tags like you own radios - Batteries, mounting, and lost badges are part of the system. A cheap tag that dies every quarter will quietly turn the map into last week's guess. Match update rate to the decision: search can ping slower than a safety zone.
Once the position sits on a live twin
This is where twinzo sits after the concept is clear. The product job is not a second location vendor. It is the live hall view that can ingest BLE, UWB, RFID, SLAM, or the systems you already run, then put those pins next to material state and production signals. Logistics uses that picture for internal logistics optimization. Supervisors use the same model for production monitoring when a line is waiting on a load that left the dock late. Capability detail lives on the features overview. A longer primer on radio mix lives in getting started with RTLS.
The concept to lock first is simpler than the stack. RTLS answers where the tagged thing is now, at the accuracy the next action needs, on a map the shift already understands. Buy that. Then let the twin carry the pin into the jobs the dock already owns.
Get in touch if you want to walk the same location question on your own facility model.