Use Bluetooth Low Energy (BLE) inside buildings, GPS on open ground, and RFID only where you need a record at a gate. BLE cards and fixed receivers locate workers room by room, or to a position within the room, where GPS signals cannot reach. GPS covers yards, roads and open sites. Passive RFID records a worker only when they pass a reader, so it shows entry and exit but not where people worked.
| Criterion | BLE (Bluetooth Low Energy) | GPS | RFID |
|---|---|---|---|
| Best for | Inside buildings, room by room | Open ground: yards, roads, earthworks | Turnstiles and gates |
| Works indoors | Yes | Poorly; the satellite signal is blocked by slabs and walls | Only at the reader |
| What it records | Room or position, and time in each area | Position outdoors | A pass through a reader |
| Typical accuracy | Room level, or a position within the room with more receivers | A few metres under open sky | The reader's location only |
| Worker device | Battery card that broadcasts an ID | Battery tracker | Passive tag, no battery |
| Site infrastructure | Receivers on walls or ceilings plus one gateway | None on site | A reader at each controlled point |
Why GPS alone fails on building sites
GPS needs a view of the sky. Once a structure has a slab overhead, positions drift or disappear, which is exactly where most finishing trades spend their day. That is why indoor tracking uses fixed receivers instead.
How BLE tracking works in SmartSites
Each worker carries a Bluetooth card that broadcasts an anonymous ID. Receivers in each room report which cards they hear, and the site gateway sends readings over Wi-Fi so positions refresh about every 22 seconds. One or two receivers per room give the room name (ZoneSentry); more receivers give an estimated position within the room (TraceGuard).
Doors as boundaries
Where an exact count matters, a door node on the frame records every crossing. An entry puts the worker inside the room and only a matching exit takes them out, and the sensor also counts people who came through without a card (GateKeeper).
Combining them
Most real sites need more than one method. SmartSites uses BLE indoors and GPS trackers, with updates about every 2 seconds, for yards, roads and open sites, all in the same attendance record.
