Locating Technologies
Infrared (IR) for real-time location: how it works, range and accuracy
Infrared (IR) location systems are a departure from everything else in this series: infrared isn't a radio frequency at all, it's light, sitting just below visible light on the electromagnetic spectrum. That difference matters enormously for how IR-based location behaves indoors, since light and radio interact with buildings in fundamentally different ways.
Key specifications
Property | Typical value |
|---|---|
Frequency/wavelength | Roughly 750 nm–1 mm wavelength (commonly around 850–950 nm for location and remote-control applications) |
Range | Typically a few metres up to around 10–15 m, strictly line of sight |
Accuracy | Effectively room-level, since IR signals don't pass through walls |
Measurement methods | Presence/proximity detection; some systems use signal strength or coded pulse timing for finer resolution within a room |
Update rate | Varies by system; can be near-continuous within range |
Tag power profile | Active IR tags require a battery; typical life ranges from months to a few years depending on transmission frequency |
How it works
Infrared location relies on a fundamentally different property than the RF technologies covered elsewhere in this series: infrared light is opaque to almost all common building materials. Where the radio waves described in our radio frequencies guide pass through walls and furniture to varying degrees, infrared light generally doesn't. It behaves much more like visible light, blocked by walls, doors, and most solid objects, and reflecting off some surfaces rather than passing through them.
This makes infrared naturally suited to room-level presence detection. A tag or badge emits an infrared signal, typically a coded pulse, that's picked up by a receiver mounted in the room. Because the signal can't pass through walls, a receiver detecting a signal is strong, unambiguous evidence that the tag is physically present in that specific room, without the risk of a signal leaking through from an adjacent space, a problem RF-based systems can face.
Within a room, some systems refine this further using measured signal strength or timed pulse patterns to estimate roughly where within the room a tag is, but this is generally a secondary refinement rather than IR's core strength, which is unambiguous room-level containment. IR is also affected by sunlight and certain types of fluorescent or LED lighting, both of which can introduce infrared noise that interferes with detection, a consideration RF systems don't share.
Measurement methods available
- Presence/proximity detection – the primary method: detection by a room-mounted receiver confirms the tag is in that specific room
- Signal strength or coded pulse timing – used by some systems for finer within-room estimation, though with limited additional precision
Advantages
- Unambiguous room-level containment, since IR signals don't pass through walls the way radio signals often do
- No risk of cross-room signal leakage, which can be a genuine problem for RF systems in buildings with thin walls
- Relatively simple, well-established technology with a long deployment history, particularly in healthcare
- Can be combined with RF technologies (a common approach) to get IR's precise room confirmation alongside RF's continuous tracking between rooms
Limitations
- Strictly line-of-sight and short range; a tag in a pocket, bag, or facing away from the receiver may not be reliably detected
- Susceptible to interference from sunlight and some artificial lighting
- Provides room-level location rather than a precise coordinate within a space
- Requires a receiver in every room or area where detection is needed, which can mean denser infrastructure than some RF alternatives
Typical applications
Infrared is most commonly used for reliable room-level presence confirmation: patient and staff location in healthcare settings, hand hygiene compliance systems, and duress or panic-button systems where knowing precisely which room someone is in matters more than a continuous coordinate. It's frequently paired with an RF technology like BLE, which handles broader tracking between rooms while IR confirms exact room presence.
Frequently asked questions
Does infrared work through walls? No. Infrared light is blocked by walls and most solid objects, which is actually one of its main advantages for reliable, unambiguous room-level detection.
Why combine infrared with RF technologies? Infrared's strength is precise room-level confirmation without cross-room leakage, while RF technologies like BLE offer continuous tracking and range. Combining them gets the benefits of both: precise room confirmation plus ongoing location data.
Is infrared affected by lighting? Yes. Direct sunlight and certain types of fluorescent or LED lighting can introduce infrared interference, which is a consideration when placing IR receivers and tags.