What Is RTK and How Does It Work?
A plain-English introduction to Real-Time Kinematic positioning, base stations, rovers, and how cm-level accuracy is achieved.
Standard GPS on a phone or a basic receiver is usually accurate to a few metres. That is fine for navigation, but not for surveying a boundary, steering a tractor along the same line every season, or placing a drone image exactly where it belongs. Real-Time Kinematic positioning, or RTK, closes that gap and brings accuracy down to one or two centimetres.
Why ordinary GNSS is inaccurate
Satellite signals travel through the ionosphere and troposphere, which slow them down by amounts that change through the day. Satellite clocks and orbits also carry small errors. A single receiver cannot separate these effects from its own position, so the computed location drifts by metres.
The base and rover idea
RTK uses two receivers. A base station sits on a point whose coordinates are known precisely. Because it knows where it really is, it can measure how wrong the satellite signals are at that moment. It sends those corrections to a second receiver, the rover, which applies them to its own measurements. Since nearby receivers see almost the same errors, the rover's position becomes extremely accurate.
Carrier phase: the secret to centimetres
Basic GPS measures the coded signal, which has a wavelength of around 300 metres. RTK also measures the carrier wave itself, which has a wavelength of about 19 to 24 centimetres. Counting whole wavelengths between satellite and receiver (called resolving the integer ambiguity) is what lets RTK reach centimetre accuracy. When this succeeds, the receiver reports a 'fixed' solution; before then it shows a less accurate 'float' solution.
How corrections reach the rover
- Radio link: a UHF or LoRa radio from your own base, good for remote sites without mobile coverage.
- NTRIP over the internet: the rover connects to a caster through mobile data and streams corrections from a base or network.
- Satellite delivery: some services such as PPP-RTK broadcast corrections via L-band satellites for wide-area coverage.
Limits to keep in mind
Accuracy falls as the rover moves away from the base, typically beyond 20 to 40 km for single-base RTK. Tree cover, buildings and multipath reflections can stop the receiver from getting a fix. A reliable correction source and a clear view of the sky matter as much as the receiver itself.
If you are getting started, the easiest route is to subscribe to a correction network in your region and pair it with a multi-band receiver. Browse our directory to compare free and paid services near you.