Locating Technologies
RTK GPS for real-time location: how it works, range and accuracy
Real-Time Kinematic (RTK) positioning is a correction technique applied to GNSS signals to dramatically improve on the few metres of accuracy standard GPS provides. Rather than a separate satellite system, RTK is a method: it uses a fixed reference station with a precisely known position to correct the errors present in raw satellite signals, achieving accuracy down to a centimetre or two under good conditions.
Key specifications
Property | Typical value |
|---|---|
Frequency | Same GNSS L-band frequencies as standard GPS, roughly 1.1–1.6 GHz |
Range | Effective range from a base station is typically up to around 10–20 km, though this depends on correction data link and local conditions |
Accuracy | Roughly 1–2 cm under good conditions with a clear sky view |
Measurement methods | Carrier-phase GNSS measurement, corrected using real-time data from a fixed base station or reference network |
Update rate | Commonly up to 1–20 updates per second on RTK-capable receivers |
Tag power profile | Higher than standard GNSS or passive RF tags, reflecting the more capable receiver hardware required |
How it works
Standard GNSS receivers measure pseudorange using the coded signal broadcast by each satellite, as described in our GPS/GNSS page. This code-based measurement is relatively coarse. RTK instead measures the carrier phase of the satellite signal itself, a much finer-grained property, but one that's ambiguous on its own since the receiver can't immediately tell which specific wave cycle it's looking at.
RTK resolves this using a second receiver, the base station, positioned at a precisely surveyed, fixed location. Because the base station's true position is already known, any difference between its expected and measured signal reveals local error sources: atmospheric delay, satellite clock and orbit errors, and other effects that are shared by nearby receivers, since they're looking at the same satellites through roughly the same slice of atmosphere. The base station transmits correction data, typically over a radio link or cellular network, to the mobile (rover) receiver in real time. The rover applies these corrections and resolves the carrier-phase ambiguity, collapsing its position estimate from metres down to centimetres.
Because RTK still relies on GNSS satellite signals, it inherits the same fundamental limitation described in our radio frequencies guide: it needs a reasonably clear, unobstructed view of the sky to work. Tall buildings, dense tree cover and, of course, being indoors, all degrade or prevent an RTK fix in the same way they affect standard GNSS, just with less margin for error given how precise the underlying measurement is trying to be.
Measurement methods available
- Carrier-phase GNSS measurement with real-time correction – the core RTK technique, using a fixed base station or reference network to correct satellite-derived position in real time
Advantages
- Centimetre-level accuracy, far beyond standard GNSS, while still using satellite-based positioning
- Works over relatively large outdoor areas without needing dense local RF infrastructure
- Real-time correction means position accuracy is available immediately, not just in post-processing
- Increasingly available as a service through commercial reference networks, reducing the need to operate a private base station
Limitations
- Still requires a clear view of the sky; unsuitable for indoor use and degraded significantly by dense urban canyons or heavy tree cover
- Needs a reliable correction data link between base station and rover, whether via radio or cellular network
- Receiver hardware is more expensive than standard GNSS or basic RF tags
- Achieving the full centimetre-level accuracy typically requires a stationary or slow-moving initialisation period to resolve carrier-phase ambiguity
Typical applications
RTK GPS is widely used in construction and surveying, precision agriculture, outdoor yard and fleet management where precise vehicle or equipment position matters, and any outdoor application where standard GNSS's few metres of accuracy isn't sufficient but full indoor infrastructure isn't warranted.
Frequently asked questions
How much more accurate is RTK than standard GPS? Standard GPS typically achieves a few metres of accuracy. RTK, under good conditions, can achieve 1–2 centimetres, roughly two orders of magnitude better.
Does RTK GPS work indoors? No, not reliably. RTK still depends on receiving GNSS satellite signals, so it's subject to the same indoor limitations as standard GPS.
Do I need my own base station for RTK? Not necessarily. Commercial RTK correction networks exist in many regions, delivering correction data over a cellular connection rather than requiring a privately owned and surveyed base station.